I personally would choose a Mac, preferably a 13 inch macbook pro, as I have found them to be more reliable than the Toshibas and Acers that I have owned. My macbook has quite often been running continously (no restart) for over a month without problems. The screens on them are decent quality, so your movies will look better than on most netbooks. The battery life is also quite good, as I have managed to get about 6 and a half hours out of the battery on mine (playing music mostly). There are two things which as a general rule should be considered before buying one, which are gaming (not applicable though as you don't game), and the price difference between a Mac and a comparable Windows based machine (Which isn't too much if you buy a decent brand, which you should be doing). Also, I think that having less problems (and the annoyance & money spending which they entail) is worth paying a little extra at the beginning.
Otherwise, I will do what the others have been doing and recommend a netbook.
