My friends often ask me "which laptop should I get for my son/daughter, and where?". So, assuming you have done your due diligence, and already read my 'Laptops Considered Harmful' posting, here goes:
SHORT VERSION: if you and/or your child are already familiar/comfortable with a Mac, then stick with that, otherwise go with a commodity brand name (I happen to like Dell and HP, and have had great experiences with both); in the UK, I always buy from one of 3: (a) John Lewis, (b) PC World, (c) Dell Direct because of decent prices and good return/replacement policies... John Lewis generally gives better extended warranties. NetBooks/iPads: great, but stay away if you want to do extended writing (more below). Be sure to test drive your choice for an extended period in the shop - take it to a table if possible to see how it feels! Don't forget to count software into the cost (e.g. student discounts for Office, required after the bundled one expires in 60 days), and since RAM is ridiculously cheap, get lots.
I'm a very long-term user of both PC and Mac, since the 'very earliest days' of both... which in one sense doesn't help readers a lot, but in another sense at least I can give a great un-biased perspective. I even use both in a hybrid form when suitable (running Windows within the 'Parallels' environment on my Mac... works fine), but generally prefer to use each on its own dedicated machine.
I use them in somewhat different ways, but my opinion is that you should:
a) place physical comfort (hands, eyes, back), speed, and familiarity (which keystrokes can you do without looking) much higher on your list of priorities than most people acknowledge (both PC & Mac are so good and powerful these days, and both have their 'down and dirty configuration weirdness', so that's really not grounds for discriminating!)
b) test drive if at all possible
The reason I mention (a) is that long-term laptop use can be tougher on your hands, eyes, and back/neck than a lot of people realise... and the 'keyboard feel and layout' is really extremely important to me. [As you can probably tell from the other postings on this site I feel very strongly about this, and advocate using little 'laptop stands' with a separate keyboard... but most students would find that horribly embarrassing, so worry about that next year.]
I absolutely LOVE my MacBook, and do lots of web browsing, iTunes/iPod/iPhoto/iPhone sync, browsing, publishing, and general emailing on it... BUT when I have some mission-critical spreadsheet, lengthy document preparation and/or high-security (virtual private network) tasks, I simply prefer to do those on my Dell Latitude or HP Paviliion laptop! [NOTE: in 2010 I migrated from a Dell Latitude to an HP Pavilion laptop running Windows 7, chosen entirely because the HP Pavilion had a decent keyboard and the shortest distance from my eyes to the screen while sitting in a comfortable typing position!].
The Mac is a more 'pleasurable' experience in the way that driving a really nice car feels more rewarding than driving a bog-standard nondescript 'vehicle'. However, there are a handful of things I can still accomplish much more quickly on a PC, and even though the 'virtual PC' on the Mac does in fact allow me to have both very nicely in one compact machine (which I do), if my life depended on it I would (reluctantly) grab my Windows laptop. I say 'reluctantly' because it's less fun, less cool (they're working on that), less pleasant - but hey, if your life depends on it, what can you do?
It's like playing electric, folk, and classical guitars... you can really 'get into the groove' with any of them (a better analogy would be something with slightly different fingerings, e.g. saxophone and clarinet), but if you're purchasing a new one you need to think clearly about which groove you want to be in.
The reality is that both (PC commodity laptops and MacBooks) are so good that for me the deciding factor is which keyboard combos and eyeball-distance-to-screen match best with the mood I'm in... they are infuriatingly incompatible in subtle ways... and if I have to do an urgent 3-hour spreadsheet job, I'm simply much faster using Excel on Windows, even though Mac Excel is perfectly good. So it depends what you want to do and what you're most familiar with.
I've mostly emphasised Mac-vs-PC and test driving, because the 'technical specs' are all pretty good, essentially, as long as you have enough memory to run things (typically 2GB-4GB RAM these days). Extra memory (RAM especially) is always good, and a ridiculously cheap investment these days. You always need more...
NetBooks/iPads: Stay away from those cute little NetBooks if you intend to use them for actual writing that lasts more than 20 minutes: you will spend more on RSI (repetetive strain injury) treatment than you've saved on the cute little NetBook. I've been through a few of those too (the original Asus Eee, a Fujitsu 'LifeBook', and a Dell Mini), and I love 'em, but they're really for niche usage (travel/kitchen/etc!) and not for long-term use. Most niche uses have been superseded by my iPad2 anyway: regarding iPads and tablets, I have long extolled the wonders of this form factor for consuming content (see my article 'Truth About The Tablet PC' from 2004). The iPad is a ground-breaking improvement on the tablet concept, but only as a 'third or fourth computer' in my opinion (laptop, smartphone, iPad-or-tablet, desktop - in no particular order, depending on your needs), and definitely not for long-term writing or content creation! I like the 'up-close' reading capabilities of the iPad/tablet form factor, but if you do a lot of typing, even with an external keyboard, you may get annoyed, and I don't think it solves the problem of 'Which laptop for a student?' However, if you want to seriously consider the iPad or a rival tablet for serious keyboard use, take at look at Walt Mossberg's video review of iPad keyboard/case solutions, and be sure to test-drive everything!
Don't forget to count software into the cost. You can get along fine with Linux and OpenOffice (which has improved greatly and does absolutely everything you need), but if you are already familiar with the Microsoft Office suite, then stick with it (student discounts available everywhere... but note that the 'bundled' version supplied with discount laptops usually expires after 60 days). Frankly, it's a political decision now rather than a technical one: If you want to support the open source / free software movement, then use OpenOffice! [But as 'compatible' as OpenOffice is, it simply is not the same as Microsoft Office which I overwhelmingly prefer].
So there you have it... this posting was written originally on a MacBook and finished off on my Dell Latitude laptop connected up to a big-screen monitor with external keyboard! In 2010 I migrated to an HP Pavilion laptop running Windows 7, chosen entirely for the best keyboard/screen-distance 'feel'... and I'm still using the same big-screen monitor and external keyboard.. the famous Das Keyboard with no lables, that I mentioned in an earlier posting.