JasonGough said:
Even if a SATA2 drives work in a PowerMac, if they're only working at the same speed as the normal SATA drives, there's not much point paying the extra money for them is there?
People often misunderstand the difference between max and actual transfer rates.
Currently, the fastest any SATA or SATAII (they're mechanically identical--only the controller is different) drive can get data off the platter is around 75MB/s. SATA I can handle at least 150MB/s (actually, I think it's 1.5Gbps, which would be between 170MB/s and 187MB/s, depending on how it's calculated). SATA II
can, but does not always, handle 300MB/s. It also can, depending on the implementation, handle port multiplication (multiple drives per port, useless in the G5) and NCQ (which usually only helps with speed on servers--on some drives it actually slows down desktop operations).
Point being that the fastest SATA hard drive you can buy won't even use half of the available SATA-I bandwidth, let alone require the doubling that SATA-II provides. The only time this could be an issue is with port multiplication or theoretical future drives, although it's worth noting that even the fastest drives in the world, 15,000RPM SCSI beasts for servers, can't break 100MB/s, and at current rates of transfer increase it will be quite some time before ANY drive can saturate 150MB/s.
So, basically, although it would be NICE to have full SATA-II on the new G5s, in real world terms it's extremely unlikely to make any difference at all right now. Buy whatever drive you want, but don't pay more for SATA-II just because it sounds better.
If you want some real-world numbers, have a look at storagereview.com -- very good hard drive analysis site.