So I've upgraded three machines to F16 (from f14) so far, two at work and a laptop at home.  The latter I spent a lot of time tweaking to work as much like my old gnome 2 setup.  XFce comes close but there are some tweaks an I have a few nitpicks.  These are my notes.

First:  make a list of all your GNOME panel-based applets and applications. 

I have a ton of menus in a panel across the top of my desktop.  I don't use the default menus much (except for an occasional use of the Applications menu).  Instead I organize my panel with a bunch of GNOME drawers, some with drawers within them.  There is no easy way to migrate these to XFce (that I know of, at least).  So I opened the properties for each applet and application icon and noted its menu position and command in  a text file.  When I got F16 up and running with a default XFce panel, I started adding these back in manually.  It's a bit of work if you have as many things in your panel as I do.  But it should only have to happen once, really.

xscreensaver can't be disabled in a session managed manner.  If you kill it, logout and login, it comes back on.  To solve that, I juse removed the package.

firefox 8 doesn't work with my old theme (Vfox3-basic, a Mac-style theme).  I found a different Mac-based theme it's not as nice as Vfox3-basic.  Also, if you hover over a link it displays in the canvas, not in the status bar, making it difficult to read if there is text in the canvas at that spot.  Finally, the bookmarks toolbar font does not match the Firefox (re: system) font.  This is probably a theme issue.  All those Firefox updates are probably making it hard for theme authors to keep up (and Personas are useless).  To bad Chrome is just as bad.  Might be time to start exploring alternatives based on WebKit.

Worse problem encountered:  CPU fans constantly running in my laptop.  I Googled for this and ran into discussions about the compositor (3d effects) causing the problem.  However, those problems were with nvidia boards and the laptop has an intel 915GM.  I turned the compositor off and didn't see much difference.  The problem was a bunch of "Tracker-*" tools that XFce started in its session configuration.  I disabled all of those and the CPU usage dropped dramatically.  CPU temps went from 179 F with the Tracker's on to 105F with them off.  Fans are also essentially silent now.

XFce has a bunch of extra utilities collectively called Goodies.  But these are not packaged together and are apparently not in the XFce group installed by the default XFce choice during F16 installation.  So you have to install them manually.  These include a bunch of panel bar applets.

• xfce4-cpugraph-plugin
• xfce4-datetime-plugin
• xfce4-genmon-plugin
• xfce4-netload-plugin
• xfce4-sensors-plugin
• xfce4-systemload-plugin
• xfce4-weather-plugin
• xfce4-wmdock-plugin

Some of the other minor nits I have with XFce:

• Panel menus don't inherit alpha of panel they live in and you can't configure them individually.  Window Manager Tweeks->Compositor "Pop Up Windows" applies alpha to menus but also to the icons in them so it's not useful for this purpose.
• The Launcher is actually used the same way as a GNOME drawer – providing a panel menu – but can't set the drawer icon without linking to an application or else you get an error if you click on it (however, you could use /bin/true as a workaround)
• Monitor applets (CPU, Network, etc) are thin bars instead of boxes.  Boxes are easier on my old eyes.
• DateTime plugin: two lines of text is annoying, no way to make it one line but it has a better Calendar than the other datetime plugins.
• xfapplet doesn't work with GNOME 3 (another reason to hate GNOME 3) and GNOME 2 applets aren't available anyway.
• Default double click on title bar for shade requires *very* fast click.  Settings->Mouse dialog: Behavior Double Click Time set to 310 seems to be a better setting.
• The Weather plugin doesn't seem to work.  It never updates ("No Data").

Worse thing that happened in the upgrade for the laptop:  The "d" key is flaking out on me.  It is a 7 year old laptop, but still.  That's the last time I clean the keyboard. 

Updates

2012-01-09

pulseaudio is not working properly and Alsa does not allow multiple applications to share audio output.  I was listening to an online music stream and tried to run Skype but the latter complained about audio problems.  The only way to get it to work was disable the online audio stream.  XFce does not have the PulseAudio configuration tool found under GNOME 2 so I could not select the application which would get the audio output.  Also, the only selection for output device in Skype that works is "HDA NVidia, ALC888 Analog".  Choosing "pulse(pulse)" doesn't work. 

X-Chat does not show up in the system tray (re: Notification Area).  No work around for that.  Bummer – I used to use the flashing system tray icon to notify me of incoming messages.

XFce's Workspace switcher bogs down badly.  I have two monitors using nVidia's driver for TwinView.  One workspace has a browser and evolution open.  Another workspace has 10-12 GNOME terminals plus a few other windows.  Moving from the former to the latter has a significant pause before changing, and the display update is very slow.  I'm not sure if this is a problem with the kernel, the nVidia driver or XFce's window manager or workspace switcher.

ssmtp has stopped working.  It's the same version as I was using with F14 and I've tried building it from source too.  Just refuses to work.  I've got suggestions to check the TCP packets to debug the problem as well as a suggestion to use msmtp instead.  Both are on my todo list.

2012-02-19

msmtp worked out as a replacement for ssmtp.  It requires only a migration of the configuration file that describes how to connect to the remote mail server.  So that's a plus.  At work, I'm generally okay with how things function with F16 and XFce, though the workspace switching delays are very annoying.

But things are getting worse.  I just upgraded my primary desktop at home yesterday after having learned to live with the idiosyncracies of F16 and XFce at work and on my personal laptop.  But today I noticed a few new things.

Rhythmbox doesn't show up in the Notification applet.  That's a bit of a pain because I control that app from there instead of bouncing over to the workspace where the window is open.

xbmc locks up while browsing videos.  I have 500+ movies on my servers at home and I watch them while I work.  The media streams over the 802.11g wireless connection.  This worked fine for F14 (and my computer hooked to the big TV is still on F14 and works fine with XBMC).  But xbmc locks up on F16.  I think this is either an issue with MesaGL or with the kmod-nvidia drivers.  I always use nVidia's drivers and not nouveau and it's always just worked.  Also, only one of the available movie players (Totem) could play the ripped ISO files when launched from the desktop menus.  I know xine and mplayer with play them but I have to launch them manually and that's a pain.  And Totem died while playing back the first movie I tried (Indiana Jones) even though XBMC always played that one without issue.

This particular issue is a major pain to me.  It's how I work at home – watch a movie while I work.  Now it doesn't work.  That's a major step back.  I seriously considering dumping fedora on my primary desktop and replacing it with CentOS just so I know it will work properly.  I've already replaced Fedora on my development server with CentOS 6.2 for the same reason. 

I know Fedora is a bleeding edge platform, but if users can't use it they're gonna lose out to other, more long term stable and supported bleeding edges.  I'm getting kind of tired of things taking a step back with each Fedora release that require special care to get back to where you were.  It's not really worth the effort, though not even this will make me move to ubuntu.