I'm a mac user since a year ago. After about 15 year of win,starting with win 3.1 on a 486 sx, with 2 Mb ram. Last 7 years spent on Dell PC's with win Xp and later Vista. I moved to mac after one year of my last Dell, an XPS M1210, that had (has, actually, still used from home) 4 Gb ram. But Vista made the trick, I was so sick of its slowness, continuous upgrades and updates, tired to being asked each day to install a system update, and after say "Install" being told that The system could not install it because of some weird incompatibility. Also, with all that RAM, the system wasn't faster than my previous Latitude 600 with Centrino 1.6 and 512 Mb ram.
Also, about the XPS: I spent for it about 2600 USD in Feb 2007. I mean, it was as expensive as the top-line MBP 15" is. SO, please, don't believe to those ads saying "PC are cheaper". I'd say there are cheaper PC's than mac. for sure. But if you want sturdy PC laptops that will work fine for a couple of years, at least, be prepared to spend as much as a mac. My wife's laptpor, for instance, is an HP 14", with 2 Gb of RAM, that she bought for 1,50 USD in autumn 2007. it costed 1,200 USD less than mine, but she keeps complaining about the slowness, short battery life (I don't think it will keep one hour on one charge), the ram cannot be upgraded...and it has Vista!
So, I think that mac OSX is far superior to Vista (I don't know Win 7, but I'll never know because I'm not going back) that it justifies a mac alone. Form factor of macs is really nice as well as usability compared to win PC's, in terms of stability, connection, durability. About restarting, I have an imac, and is on 24 hrs per day, 7 days per week. I only restart it when system upgrade require that. Maybe two times per month?
Oh, and I never had any freeze of the whole system, requiring a reset.
But, maybe, I'm just a lucky guy...