I have a verdict as if my judgment matters. Ubuntu 11.04 Natty Narwhal is fine until you consider the new Unity desktop. First of all a "default desktop" should work on the meager hardware and on the well endowed. Unity has behavior problems on the low end, it is not a light weight solution and maybe it is not meant to be. Installing Unity 2D allowed it to work on my laptop fairly good. The slowdown comes when graphic intensive apps are used. Could be just a hardware issue. I installed XFCE desktop, it works way better than Unity on my laptop.
Then there are things missing so that adjustments can't be made to closer match my way of working. Unity is more a touch screen interface than a mouse driven desktop. It recalls what is seen on many hand-held devices these days. The touchpad on my antique laptop is disabled because it is awkward to use, unstable, too touchy. Perhaps new devices are way better.
Unity is habit forming which means, I like it enough to keep playing with it. I hope it will improve. I also used Ubuntu Classic in Natty. It is flawless and is about to succumb to evolutionary changes into Gnome3. Gnome3 is similar to Unity with transparent layers, floating icons, retracting panels. I think KDE started this dashboard madness and incorporating compiz. The Linux folks are trying to prove they can deliver innovation and style as well as Apple and MS.
There is simple, there is sophisticated, and now simply sophisticated. How many functions can you put behind that big on off push button? Time will tell, things will change and we will change too. You say no!? Eyeglass cleaning tissue got killed by contact lenses, got relabeled as hand-held device display cleaning tissue.