I just built 2 systems the past week. One with the IBM 60GXP and the other with the Seagate Barracuda IV.
The IBM is extremely quiet, but nothing like the Seagate. I have 'silent' fans and HSF in both computers and it's impossible to hear the Seagate except during very, very heavy seeks. And even at that, it's barely perceivable. The only way to tell if the Seagate was working was to check the HD LED.
Unfortunately, I only ran HDTach on the Seagate which brought in an average transfer speed of 30MB/sec on Win2K SP1 with no VIA 4 in 1 drivers. (I have an Appollo Pro Chipset for P3.) Just as a comparison, my Quantum Fireball LM brought in an average speed of around 23MB/sec. Both these numbers seem kind of low to me, but it could be the older chipset and not the latest .inf files. (I'm still in the process of updating my system so I'll post the new numbers later with the latest drivers. But no 60GXP since I had given that to someone else.)
I can't compare usage since the IBM when into an Athlon 1.2 GHz and the Seagate into a P3-733. But when I build the next system for someone, I'll be sure to put in the Barracuda into them. It just seemd slightly more responsive (faster seeks?) and of couse, virtually silent.
Also, I did a touch test on the hard drives to check the temps. They were both warm to the touch but nothing that I would be concerned about. I couldn't really tell the difference between the two, but they were both warmer than the Fireball LM.