SCSI is still useful in a datacenter enviroment. For one IDE drives are not nearly as mature for hotswap.. Good luck finding hotswap subsystems for UDMA that actually are reliable and work well, if you find one let me know. 😉
If I had a few extra bucks I'd jump on this quick. I'd get 3 or 4 of these, go RAID5 for just a little over the price of a 180GB IDE, but be WAY quicker by a magnitude of 2 or 3 times. Plus I'd be safe from a single drive failure.
I personally don't use that much space (40GB max, that's with a lot of crud laying about) on my home system(s). Data archiving for me is all done at the datacenter.. Just so much easier. Even then, I'd buy this SCSI setup, then wait for the maxtor 320's to come out and grab one of those for mp3/video/etc. storage that doesn't need fast random access.
My home setups are ALWAYS expensive(r) smallish drive for OS/apps, and cheaper large drive(s) for data archiving. If you think about it, you'll be extremely hard pressed to even fill up 40GB, much less 20GB if all you put on it is your OS and applications.
-Phil