I recently upgraded to Ubuntu 11.04, complete with its new "Unity" desktop. 

A lot of people have been crticical of Unity, mainly because it's new and some people just don't like change. I've been using the Netbook edition on my netbook which already had Unity as the default so it wasn't new to me.

After a couple of weeks of running 11.04 I noticed that I'm spending an awful lot of time waiting and watching the Hard Drive LED glowing. I've switched back to Ubuntu "Classic" (i.e. Gnome) with the Cairo Dock and my computer once again seems lightning fast.

Clearly Unity has some memory issues that need resolving- I hope before 11.10 is released.