As with all technology, when it works it's great, when it doesn't it is really, really bad. Seagate lately has had a batch of hard drives released that have had issues with their firmware. They announced this after I had gone through about five of them, and some customers of mine had gone through two or three more. Since they're under warranty I can have them replaced, but I won't get back my time rebuilding my RAID array and those of my customers. Because of this, I have switched to Western Digital for my future hard drives and those I recommend. The new drives run in SATA generation 2 instead of 1 out of the box, they seem to be faster, and I haven't had any issues with them.
The main reason I had stuck with Seagate for so long was their warranty of 5 years, but now that WD has that too I can switch away without worry. The issue, my friends and I think, is the substandard manufacturing plants that Maxtor had. Seagate bought Maxtor a while ago and we all knew at the time that Maxtor sucked. The sheer volume of Maxtor drives going through my friend's shop for repair (i.e. replacement) was proof enough of that.
I have kept an eye on the new SSD's (solid state disks) that are creeping down in price. The good ones are still very expensive, but in another year or so things are going to start shifting away from the old hard drives. I look forward to the speed boost that should bring.