I've installed Centos 5.2 on a dual Xeon box, and as far as video support I can't get the resolution to go higher than 1280x1024. It will let me set it higher but it freaks out and distorts the video. However, on another box with a AMD Athlon P2400+ processor and NVidia GeForce4 MX440 it works fine in 1600x1200 mode. It may be that the video card on the other box is not capable of higher resolution and other than that it seems to work fine.
I've installed Shockwave and some other browser plugin's with the Firefox 3.0.1 it came with and they all seem to work fine. It seems to keep up with real time full motion video fine. So I'm not really sure what the issues other people are having with video support are.
I've got Xen installed and have it running a hypervised kernel but I haven't any virtual machines running yet but I'm pretty sure that's an operator error issue. The instructions aren't the clearest and neither am I.
It does seem extraordinarily efficient in it's use of memory. With a hypervised kernel, Xend, X-windows, Firefox, a terminal window, (Gnome window manager), various toolbar applets, and the usual assortment of Linux background daemons, font server, etc, it uses about 308MB of RAM. My Windows XP box uses more than that for just a single user running Firefox.
The only thing I really dislike is the use of Disk Druid which insists on re-organizing the partitions the way it sees fit instead of the order that I want them on the disk. I put things on the disk in specific order for a specific reason having to do with the fact that the outer tracks of the disk are faster and therefore speed critical things like swap and the most frequently used binaries should live there, but Disk Druid insists on re-ordering them for me.