I would just like to say that we have gotten much faster HDs than what you portray.
146GB, 10000RPM, ~6ms, ~70MB/s, and 73GB, 15000RPM, ~5ms, ~75MB/s.
The difference is that the RAM in servers only costs about 40% more than what's in desktops, assuming 1GB amounts (for 512, the difference is even less, closer to 25%), as that's about as high as most resellers have. Hard drives in servers start at 100% more and go up, not counting controller and cable costs.
Also, when command queuing starts to get used, SATA RAID 5 will be an excellent option, as seek times will begin to matter less than they do now, and you will still get an excellent speed increase (BTW, RAID 0 can not change access times).
I agree, RAID is not the solution to the hard drive problem; but brining technologies long used in SCSI to commodity drives is an excellent solution.
My last criticism is that many of us now have mice with no moving parts, even relays, bringing the mechanical count down to keyboard (some don't have "moving parts" technically, but mine sure does), HD, optical drives, and most monitors.