I have been running Ubuntu for several years now, and to be honest I havenít looked back. I just find it a much more comfortable development environment as opposed to Windows.
Dataguy touched on Speed. It is very true that most Linux distros will easily run on older hardware. The common scinario would be a user who is getting a new system and decides to run a version of Linux on his/her older system. I encourage this because it can be a real eye opener just what a user can do with Linux.
If however you are a full time Linux user, then new hardware running Ubuntu is awesome.
Duel boot is a real option, especially is you NEED applications that run only on Windows OS.