First of all, congratulations to all those involved in the new release of Ubuntu (yes, including Debian folks): it seems to me that this is being one of the most mediatic GNU/Linux distro releases, and every comparison between Ubuntu/Mac OS/Windows I've read so far tells me that this new Ubuntu release is doing well.
Still, here are some critics...
I'm a fan of Debian, not really a fan of Ubuntu. Probably my biggest pet peeve with Ubuntu is what is somewhat described in this image:
Some people don't understand why do I consider the fact that in Debian each package has a maintainer a good thing, compared to Ubuntu's anarchy. Here's a patch that I just saw and that explains one of the things that might happen in result of such lack of control: In this first pach to geneweb , we see Ubuntu forking Debian's package. In other words: Ubuntu folks used Geneweb's Debian package, but there was something they wanted to change, so instead of reporting a bug to that package, they just fork'ed it and created an Ubuntu version of the package. Now let's see what is that change about: reading the patch you'll easilly understand (even if you don't know nothing about code) that this patch is made to avoid a bug in pkgstriptranslations, a package and software created and maintained by Ubuntu. Now, why the hell are Ubuntu folks writting workarounds in other software instead of fixing their own bugs?
And there's the "you should keep your mouth closed" Gobuntu issue. So, Mark Shuttleworth announced that Ubuntu “Gutsy Gibbon” would be available in a super-strict, 100% open source flavor (now called “Gobuntu”). Well, that's nice and all but... Gobuntu has non-free contents ! If you don't have the guts to go without non-free (and yes, it is a question of guts since the issue involves pissing off Mozzila Corporation), why bothering creating Gobuntu? After all there's already gNewSense ...
Finally, I'm still pissed off with Canonical because they're failing their yet another long-time-ago promise: to "fix" the "mistake" of forgeting to give credits where credit is due, namedly on the fact that Ubuntu can't live without Debian. Yet, they keep forgetting ...
Now, don't take me wrong, I'm glad that Ubuntu exists, they pushed the boundaries and forced the whole bunch of GNU/Linux distros to evolve. Their bug #1 is something I want to see fixed  (specially when phoning to several laptop vendors like ASUS and LG Electronics just to get a reply "no, you can't but one of our laptops without Microsoft Windows"). Ubuntu has a lot of cool stuff: I'm still waiting to see Debian LiveCD  promoted as an excellence way of testing and installing Debian as Ubuntu's LiveCD is, for instance... But there are lot's of important issues to be addressed, more important (in my oppinion) than just "going bleeding edge and work on the hype".
 - http://tinyurl.com/2fkwwc
 - http://tinyurl.com/373vhk
 - http://www.gnewsense.org/
 - http://www.lucas-nussbaum.net/blog/?p=257
 - https://bugs.launchpad.net/ubuntu/+bug/1
 - http://live.debian.net/