This is my latest play tool. I've been working with ROS for about 2 months now. Heard about this great meta-operating system (as it is called by its creators) from a friend @ work.
Installation of this massive library was rather uneventful (thank god!!!) on my Ubuntu 10.04 machine (back then). Just followed the ros wiki site blindly.
http://www.ros.org/wiki/cturtle/Installation/Ubuntu
I recommend usage of the ppa for all future package management through the Software Center.
ROS has got by far the best support for this os. So, i truly recommend usage of Ubuntu 10.04.
My ROS installation however ran into few problems when i upgraded to the latest Ubuntu 10.10. ROS.org doesn't as of yet support this OS if upgraded from 10.04 (ROS installation may break on upgrade) . However, i've found their latest build on their svn repo to support it (OOOohoooo) !!!. If installed using the svn repo, u will however not have any support from the ubuntu software center w.r.t the ros package management (pretty obvious stuff).