I'm pretty happy with 5400 on my other notebook so I imagine that it would be fine on the A64. I do a lot of stuff on an external drive and use a RamDrive for various functions and have the pagefile turned off which alleviates some load on the disk.
Having a few hundred MB of memory available as a disk cache should beat 8MB disk cache. BTW, memory management on Windows is much better on Windows 64 than it is on Windows 32.
"Even a 5400 rpm disk would have made my bad news list unless it had an 8MB cache."
5400 rpm with a 2MB cache made a substantial difference on my r3000z. I don't think that a 7200 rpm and/or 8 MB cache drive would have made all that much difference. I snagged a 40 gig., 5400 rpm drive off of ebay for $74 and have been quite happy with it. Now if I could only solve the problem of the wireless under 64 bit Linux, I'd be a happy camper...