I recently installed Ubuntu on a Lenovo G555 because I was having problems with the Squeeze network install CD (the laptop's ethernet cable kept on disappearing!).
While I usually prefer Debian to Ubuntu, I appreciate some of the things that Ubuntu has done for GNU/Linux, including the awareness it has raised for the operating system and kernel. I use Debian on my current laptop, and really like the setup: AwesomeWM, some GNOME components, Iceweasel, jEdit, Vim, OpenOffice, and Chromium.
I decided to stick with Ubuntu for the G555 as I read that it was easy to use the Broadcom binary blob for wifi networking. It was indeed, and it was also easy to setup the ATI binary blob for video.
For the most part, I'm quite pleased with Ubuntu. I'd tried it before, but decided to switch back to Debian as I wasn't crazy with the use of Upstart instead of the normal init system. I didn't happen to think that the issues with init were worth splitting from Debian efforts. Years later, Ubuntu is still using Upstart, so apparently its stable enough to trust. Ubuntu is now version 10, and it looks and feels quite nice.
I'm surprised that it still uses Grub legacy instead of Grub 2, like Debian Squeeze is now using. Thankfully, Ubuntu comes with Firefox 3.6.2 (3.6.x is in experimental on Debian). I also noticed that ext4 is the default filesystem. Just in case, I decided to switch it back to ext3.
There are some interesting differences between Debian and Ubuntu - seems to me that Ubuntu is focused on making GNU/Linux more appealing, while Debian is focused on making it better - both valiant efforts!
Also, the Lenovo G555 is an great machine except for the fact that the ethernet device keeps disappearing on me!