I just got an E6500 laptop from Dell with Win 7 Professional, so far running very smoothly, I love the windows snap features, very useful for file manipulation, sorting etc. I don't think I've ever used the windows key on the keyboard as much.
I recently purchased a notebook.. im using Windows XP Home edition.. Im just thinking maybe with a notebook, XP is a good option! I havent used Windows7
For longevity sake, I probably would opt for Windows 7. XP is old in the tooth, and now that MS have released a successful OS (sorry, Vista), its days are numbered.
There's a chart here showing what features the Starter edition is missing: