Basically, from all the above it seems that most modern HDDs are pretty reliable solid beasts. For every "My Seagate ate my children" type complaint you'll have loads of satisfied customers, similarly with all the other brands. I run a pretty good mix of all these drives at work, mainly SATA types in both PCs and smallish (< 2TB) servers - grownup Servers are still largely SCSI, though that might be changing.
Although it sounds a bit counter-intuitive HDDs just love running and running. Most of the stress on the rude mechanicals is when you start them from "cold", I'm sure this is one of the reasons that PC and laptop disks tend to fail more than server disks. Of Course server disks tend to be "better" to start with!
The other thing they hate is extreme temperature fluctuations or running very hot (or very cool). 30-35C is apparently a good range, though modern disks are so bloody good I think anywhere from 20 - 45 (measured on the disk) will be OK.

I currently am a big fan of both the WD "Green" disks and Samsung's finest, with Seagate's "Enterprise" quality disks on my SATA RAID arrays, but (touching wood etc) its literally a year since I've had a HDD failure, and that was on a server that ran 24/7 for nearly 5 years.....

I tend to agree. I had one dodgy experience with Maxtor but that's it. Now, it's not so much about the reliability as it is about speed/quietness/etc.

At the moment for new builds it would have to be W/D.

Seagate had that issue with their 7200.11 drives that were dropping like flies - failure rate I saw quoted was about 40% Whats more criminal is that some places I've seen are still trying to sell them and not their replacement (7200.12)

Samsung not much better with their 1Tb F1 drives also failing at a higher expected rate.

Just had my 2nd Samsung die on me in last 6 months so not going near them for a while.

samsung all the way