ibooks/powerbooks are quite quiet... I leave mine on all night, while my BF turns off his PC because it is a crazy loud monstrous machine! but this thing is whisper quiet.
Ibooks are great, but ALWAYS upgrade the ram. you should have a minimum of 512mb of RAM. OSX is really designed to run off of nothing less. and while I never recommend buying cheap ram, dont get it from the apple website because it is so over-priced.
everything said and done, I payed about $3000 cnd for my laptop after taxes and a ram upgrade. I have a combo drive, not a superdrive, sometimes I wish I had the super but my friend's powerbook overheats when he uses it (mind you, it is a first generation superdrive)
my favourite feature of the OSX software is Expose - other users can probably attest to this, but if I have 80 pics in photoshop, I just drag my mouse to the top right corner of my screen, and expose 'tiles' everything for me - creates small icons of everything so it can all fit on the screen at once. 80 windows open on an XP machine would be too much because you would have to click through it.
if you are just looking for a laptop for papers and such, I would get the 12 inch ibook, with a ram upgrade. you can get the full suite of microsoft office software for mac, the main compatibility issues lie in games - there is a LOT of software for macs. the 12 inch size would probably be ideal because it would be easy for you to tote to classes if need be, pop it into a bag, and you are not as much of a theft target with a laptop bag - any messenger bag will do, just get a 'wallet' for the lappy to prevent it from scratching.
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