Work just purchased a new development machine for me. I was given free reign to choose whatever I wanted to work on and I ended up going with a IBM/Lenovo t42 laptop and putting Mandriva 2006 on it. The whole experience was delightful. Linux runs absolutely great on it. The wireless was picked up right away. Everything just worked.
There were a few small edits that I had to make to complete the package though. It needed some tweaks to the laptop-mode settings. I also had to edit the acpi script for closing the lid so that it called suspend properly.
A very good choice for a system if you’d like to try putting linux on a laptop. Very well supported.