Well here are some tips that you might find useful (although I don't have a laptop right now, because I want to wait and see how the tablet PC's faire, I used these tips when I was just looking around)

Since dual-core technology has evolved so much, I would might as well go for a Dual core processor (perhaps AMD Turion 64/ Athlon 64 or the new Core Duo's). The main reason for this would be that you can do a lot of multitasking since you have twice the power, so one core handles a few tasks and the other part the other tasks.
And try to get a laptop with a big hard drive if you can... (try to keep it 80 Gigs or so... the more the better) because if you want to add more space in a laptop, it's a bit more harder. Get a laptop with adequate memory (at least 512 MB, which is standard) and try to get a laptop with a considerably good video card since you aren't going to play any games. And make sure that you get a laptop that is sort of like the standard laptop (has features such as wireless b/g)

Oh yeah and don't forget to get one with a good battery life, since you wan't to watch videos, battery life is key. And remember the bigger the screen the heavier the laptop and the more battery it eats up, so I would go for a mid sized say... 15.4 screen.

If you wan't to get a Mac, I'd say that you go for it... because one thing's for sure it's better than windows based PC's. But like William said the Price tag might be a bit to big... But basically try to get a laptop within the price range of 800-1500... I wouldn't go any lower because, as technology evolves you don't want your laptop to become useless (this might not be true if you don't plan on upgrading too much).