I have 5 Hitachi drives (a 2TB external, 2 each of 1 TB & 500GB internal). None of them have failed on me since using for 3-4 years. The 1 TB drives run a little hot as they were the 1st gen 1TB drives, with 5 platters. I agree with the above post. Every manufacturer has bad products once in a while.
IMO, irrespective of manufacturer what matters most when considering drives for a NAS are the number of platters, spindle speed i.e. RPM, price, power consumption and acoustics. Number of platters is a double edged sword. One one hand it decreases power consumption as the motor has to move less mass. The downside is that data is packed so densely into the disks that the servo control of the drives has a hard time reading and writing data. Lowere RPM is a big plus. It reduces heat and is more silent.