I like the Hitachi drives. They are fast and ultra quiet. That said... every single one I have bought has failed at about one year. Fortunately they carry a three year warrantee and Hitachi is very good about the warrantee if slow. Keep another drive around, which you should anyways for backing up yoru data, so that when you have to send in the Hitachi you have something to run from. The good news is the replacement drives Hitachi sends me have never failed (yet).
I also have Fuji (loud), seagate (good), Maxtor (new ones are excellent, fast and quiet but I used to have trouble with them and hear of others having trouble), Western Digital (good drives but the power supplies fail in every external WD drive I have had, usually out of warrantee, sometimes in) and some others of less mention.