I'll keep this entry short and sweet.
I spent a little time installing the latest versions of Fedora (beta) and Ubuntu (final). In both cases, the distributions failed to fully allow Virtual Box guest additions to function in a virtual machine, especially seamless desktop and automatic desktop resizing. I'm not worried if those specific releases fully work. I've trimmed my VM "offerings" to RHEL 6, CentOS 5.6, Fedora 14, and openSUSE 11.4, which work just fine in Virtual Box 3.2.12.
Ubuntu is headed down a path that I don't believe is supportive of the lab's current capabilities. I may change my mind once the lab has migrated from Virtualbox to VMware Enterprise. If the same (or equivalent) features are available and if I can virtualize Linux distributions on VMware Enterprise without having to do the kernel rebuild dance every time a given distribution pushes out a kernel update then I'll be quite happy. The notable exception to the kernel rebuild dance under Virtualbox is openSUSE 11.4; I've never had an easier time of virtualizing a Linux distribution under Virtualbox, and every time the kernel was updated, the VM continued to work.
I've tried to maintain an open mind with regard to the two new desktops, Gnome 3 and Unity. After an admittedly brief exposure to both, I've decided I don't care for either. Unity won't run at all under Virtualbox and defaults to an older version of Gnome 2.x. At least that leaves you with a working desktop. On Fedora 15 beta, there is no default Gnome 2.x desktop fallback. Instead, bits of Gnome 3 fail to operate (such as the panels).
I installed Fedora 15 beta a second time with the KDE 'software compilation' to provide a working 'workspace', a.k.a. desktop, that I could deal with (a bit of irony in all that). With KDE I was able to fully configure networking, something that I found impossible to accomplish with Gnome 3's equivalent beta tools. In the end KDE proved annoyingly alien enough that I scrubbed the Fedora 15 instance, along with the Ubuntu 11.04 instance.
I've scrubbed all Ubuntu instances because we use Chrome, and both installing and maintaining the latest Chrome (and Firefox) versions on older Ubuntu releases turns into something of a non-standard maintenance process. And I loath non-standard.
This is not to unilaterally trash either Ubuntu 11.04 or Fedora 15. Just because they don't work in this particular environment doesn't mean they're somehow a complete and utter failure for every environment. With Linux, through Linux's diversity, I'm looking for a reasonable balance between guaranteed reliability (RHEL) and low-risk experimentation (everything else via virtualization). There's no reason for anybody to become upset over my opinions or my results. On the other side of the Linux debate there's no reason for anyone who likes to hate on Linux to hold up these results as bolstering their hating ways.
I have had more than enough successes with Linux. Linux is a means to an end in my life. Life is too precious to waste wrapped around the axle over an issue or a perceived slight against some Linux sacred cow. Life needs to be spent doing something truly productive and enjoyable.