The 60GB IBM (8MB/5400RPM/9.5mm) is a very good performer. We've used it in many Pismo/older TiBook upgrades (some dozen or so) and they've all worked flawlessly.
I use an 80GB IBM (8MB/4200) in my PB 12, but I did that because of two important factors:
1.) Heat. The 4200RPM drives are hot enough in my little PB, I'd hate to see how hot it would get with the faster 5400RPM drive.
2.) Space. I wanted storage capacity more than I wanted performance. I was pleasantly surprised though. The 80GB IBM is quite a bit "zippier" than the 40GB Fujitsu that was in my PB. I attribute this to the larger cache (8MB as opposed to 2MB) and increased areal densities (twice the storage on the same amount of platters).
Anyway, it's really hard to go wrong with the fast 60GB IBM in your Pismo. I highly recommend it.
