Well, a few things:
Look at the
specifications for the test system that Canonical used for this study. This is a typical Lenovo business laptop with fairly high-quality components, but the IGP is an Intel "HD Graphics". This tells me it's in the G45 family most probably, since the i3-370M is not a Sandy Bridge CPU. So this Intel IGP is in its prime right now: Intel has had years to work on the G45 generation's drivers; Intel IGPs continue to be immensely popular; and it has all the hardware features you could want for supporting something like Unity. It's a much more advanced chip than the 965G generation that preceded it, and it's been on the market much longer than the Sandy Bridge chips that, if they had used those, I'd have understood the crashiness to be a driver problem this early in the SNB game.
But, I've been running Fedora 15
Alpha using Gnome 3.0 and Gnome-Shell on my Lenovo ThinkPad X61T for close to two weeks now. The only things that have crashed are the Humble Indie Bundle games, and PulseAudio. Gnome-Shell has
never crashed, and the PC has been on and in-use 8 to 20 hours per day. I'm using the open source graphics drivers on the 2.6.38 kernel, just like Ubuntu Natty would do. What's the difference? No Unity, no Compiz -- Gnome-Shell and Mutter instead.
The performance is also fantastic, even with the X61T's aging 965GM chipset. Transitioning from a maximized browser window to a gnome-shell window present (tap the Super / Windows key, similar to Unity) is smooth as silk. Now on my Radeon HD5970, the same transition does lag a bit sometimes, but I chalk that up to performance issues in r600g yet to be resolved :P
But on both chipsets, with Unity, I can get the same rate of crashes, drops in FPS (noticeable lag when hovering over icons), and lag when viewing the "Present" view of open windows, as reported in the usability study. So I'm basically one more person able to confirm the problems with Unity, and I've tested on both r600g and i965 classic.
And don't think the binary drivers are any better, either. ATI's support for Unity in Catalyst is still pretty rough around the edges; they made a release specifically to get it minimally working on Unity, but they admitted that there are still defects and crashers present. I've tried the same Catalyst driver on Fedora 15, and while still being woefully proprietary, it does indeed work well with Mutter and Gnome-Shell.
I can't speak to the NVidia binary driver as I don't own an Nvidia card.... but if the Nvidia binary driver is the only driver that works well with Unity, that's still a really big problem. The percentage of people who (a) have an Nvidia card and (b) know how to get the proprietary drivers working is probably about 20 - 30% of all Ubuntu desktop users, conservatively. Don't believe me? Look at the past Phoronix Linux Graphics Surveys, where some 80% of users just run whatever driver is installed by default in their distro. What's that for Nvidia cards? Nouveau, am I right? How well does Nouveau cope with Unity? Fermi cards?
All that aside, I 100% agree with you that Unity
can rock. Any software can be trivially said to have the potential to be excellent at some point in the future, because no software is ever barred from the possibility of future enhancement, refactoring, etc.
And indeed, Unity is already doing things that would predispose it to rock in the near future. But will it be near enough for Natty? I still have my reservations!