Vista,
This OS, has undoubtedly caused the biggest stir. Because of Vista, Apple, have sold twice as many MACS this year, as they did this time last year! Now there's food for thought.
I'd recommend Vista, but with a couple of caveats. Vista, NEEDS resources, 2GB of ram is fine, and will do the trick nicely.
What you now need to look at is what Graphics Chip the Laptop Has....(hard to explain this one). Basically, look for one that has either ATi, or Nvidia Graphics Chipsets. Motherboard Manufacturers Graphics, I.E Sis, Via etc....not enough power behind it.
I'd say go for ATi, they seem to have been the most Vista Ready since the get go. However, thats down to personal preference, so is the processor.
I'd say, look for a laptop, that has, 2GB of Ram, A Dual Core Processor (AMD or Intel) then the "Branded" Graphics System, Ati or Nvidia. If you get a laptop with an AMD Dual Core, Get the ATi Graphics, if you get an Intel Model, go for the Nvidia Graphics... AMD own ATi now, They are the best optimised integrated systems at the moment! and Vista Home Premium (Not Basic)
If you get XP Pro, then really, as long as you have a tleast 1gb or ram for all your programs, your laughing...
however, Vista is becoming more standard now, as there's only a few things that may not work with it, with a laptop, all your drivers for the laptop will work...SP1 is supposed to be coming out November time only 3 months away.....which is when everybody will start buying it...if you buy XP Pro Now....if you decided you want Vista Later on....thats more money out of your pocket.
Cheers