I finally bought the Barracuda V 120GB - as a replacement of my Barracuda IV (80GB) - after trying out the new WD special edition drives.
I have tried one WD1600JB (160GB), and 2 WD1800JB (180GB) - all with 8MB of buffer. I returned the first 160GB and 180 GB because they were noticeably louder than my cuda IV , the last 180GB was more quiet than the other 2 but died on me after 8 days (a rattling noise for 15mn then goodbye).
So I decided to go with the new Barracuda V.
So far I have it for a week and I am very happy with it. It is extra quiet (even more than the IV and even while seeking with the noise reduction on).
For what I use it for (I do compile very large programs - more than 3000 Java classes - on it), I did not see any difference with the WD drives.
The WD drives look nicer on the performance graphs but for me (and probably for most users) that's not perceptible at all.
I hesitated between the Barracuda V and the IBM 180GXP but sided for seagate for its lower noise and my good experience with the IV.