I've used an old Vaio 505 for a few years and it has worked well - other than its appalling battery life. I believe that this has been fixed on newer machines.
I've also used Toshibas extensively and would never spend my own money on one. Yes I know this is subjective but there you have it
Currently use a Tosh Tecra 8100. Had one hard drive failure and the keyboard is prone to self-destruct. Used to have a Portege 3110CT and it had a low res screen and a dodgy hard drive. Used to use a Tecra 900, which was terrible. You get the picture. I'm sure others love them but I don't.
Concerning XP, go for it - if you don't need Win9x for compatibility reasons, there is no reason for an end-user to pick Win NT or 2000 over XP. It is solid and as long as the machine has a decent spec should run OK. Also it handles wireless networks well.
As is usually the case with computers, go for the best that you can afford - it will be next year's entry level model but at least you'll be able to next year's software acceptably.