Reading the replies to the post about a global menu from xfce257, which suggested an application was having trouble because of an old version of gnome panel, brought to mind an article I read lately suggesting KDE was the natural place for disaffected gnome users. It indicated XFCE would run into problems because is was still based on Gnome 2, which as time went on applications would no longer support. (Yes, I know it's gtk+, but the article said Gnome. Sorry, I looked for a link to the article before posting but didn't find it.)
Anyway, how much of a problem is sticking with gtk+ 2 likely to be before XFCE switches, which if I recall correctly, Nick indicated in another thread was likely at least a year and a half away, not planned until XFCE 4.12. So far I haven't had any personal problems with apps (running Deb Testing with an XFCE DE on my main desktop at home) and it's hard to imagine developers will ignore a toolkit which will, a year and a half from now, still be used in Mint 9, RHEL/Centos/SL 6, Ubuntu 10.04 and Debian Squeeze, all of which will still be supported a year and a half from now (though the support for Squeeze might be as oldstable by then.)
Also, is there likely to be sufficient impairment in function, or additional bloat, when XFCE switches to gtk+ 3?
one of many happy migrants from Gnome 2
Until now there were no attempts to port a core application to gtk3 for testing, but I don't think here will be much of a difference compared to gtk2. Overall gtk3 is a nice cleanup over gtk2 with numerous improvements. It also features some new widgets that are more suitable in the new gnome3 interface then they are in the old-gtk2 look, but that might just be a matter of taste.
So without trying, gtk3 looks promising, but it will take some time to make it work, because radical changes were made.
My personal oppinion is:
fir migrate independents parts like: Mousepad, XFPrint, XFburn, the GUI of XFconf, Ristretto....
and before this use the other components
and in the other part the themes, your migrate to gtk3 all the themes or make nows themes???
XFCE 4.10 :: Arch Linux
:: Intel(R) Atom(R) N2100 @ 4W at 1.60GHz but running at 0.3-0,7W at 600Mz)
:: Intel Graphics 500/ Poulsbo
:: LED WSVGA of 10.1" (1,024 x 600) anti-reflectant