Seagate seems to have the best warranty in the Biz right now with 5 yr warranty on their drives. Cant beat that anywhere... In my experience any warranty over 3 years is amazing.
As an Apple tech for a school, Ive seen alot of drives fail within 3-4 years or less: So that warranty is a HUGE selling point for me.
My Roomate fried the board on his Drive by plugging the wrong Power adapter into it: seagate replaced the drive.
Just for Refrence: Seagate has Bought out Maxtor...hope that helps out Maxtors reliablility: Press release
Seagate designs their drives with quiet in mind. Every quiet pc recommendation has recomended seagate. They also have the best warrenty, so best of both worlds.
Yes seagate has a reputation of being quiet but keep in mind there are quite a few models of late that have not been so quiet. I have a 500GB seagate 7200rpm ide and a 160GB seagate sata, both are loud then the much older seagates. There are lots of online reviews that can attest to that. Right now, samsungs are the quieter ones to me.
As for the new iMacs, my 20" Intel has a WD in it and it is very quiet and so far fast. I'm not sure if that's across the board thought as maybe some others can do a check on their iMacs and see what brand they have.
I use a Samsung 160GB drive in an external enclosure and it's rare that I even notice the thing running. It is pretty fast and has been quite reliable. Not to mention it runs pretty cool for a 7200RPM drive. I plan on sticking with their drives for a while to come.