I finally upgraded to a 10k RPM drive, recently, and I was impressed. I ended up getting the 36 gig version though, and using a 7200 RPM drive for sotrage of data and such. Besides size, the only other downside to the 36 gig, is the lack of native command queing.
I guess it really depends on what kind of system you are building.
If you are trying to get by reasonably cheap, I would go with the 36 gig, and use another drive for storage of data, and extra space for games if you fill up the 36 gig.
If money doesn't really matter, go with the 74 gig drive.
My Desktop: <A HREF="http://Mr5oh.tripod.com/pc.html" target="_new">http://Mr5oh.tripod.com/pc.html</A>