.... whilst P2011.1 seems more like a testing version.
I don't agree on this ^^^ one.
On my little netbook P2011 does perform equivalent to P2009
I reloaded my image of P2011.1 on my laptop and surprisingly, if I enable Desktop Effects/compositing, the GUI is much smoother when moving windows etc. I haven't got enough memory to keep it like this though so will have to run it with Desktop Effects/compositing turned off and put up with the edges off windows breaking up when they are moved. Must be something to do with Kwin I guess because this doesn't happen with P2009.2 which is using the same graphics driver. Overall, 2011.1 is much more resource hungry and runs quite a bit slower on my machine than P2009.2. Plus, P2011.1 will not install, I had to install P2011 and then update to P 2011.1.