Earlier quoted context omitted.
In some respects - I switched from GNOME to OS X and I found that Nautilus respected the tree a lot more than OS X did, NetworkManager also showed signal strength before OS X's top bar network thingy did. Only reason I quit is that after speccing hardware that had OSS drivers (and was fairly underpowered to boot), drivers in Ubuntu still didn't work 100% (eg, connecting to external displays broke X render support) an…
(Intel drivers being replaced with much more unstable replacements). Ugh, I had this same problem. Every time I upgraded Ubuntu, hardware rendering got another 10x performance decrease and more bugs. Eventually I couldn't even enable vsync, so I got horrible tearing while watching videos. I partially blame Ubuntu for this, since they could have held back Intel's driver updates. Ultimately though, it was Intel's fault…
Switching acceleration architectures to something that's not from the '80s, allowing modern hardware to effectively accelerate the UI, allowing video to interact with OpenGL and so on needed to be done, and there was really no good way to do it painlessly.