for what it's worth, my 2008 NT maps arrived today. i doubled-clicked the install icon on the CD (after inserting it into my Mac). i was using OS X and not parallels. it had me enter my serial number, which i did. 23 minutes later the update on my Garmin i5 was complete. in other words, a PC was not required for this new set of Maps. i imagine the PC is required for the older maps folks here have used in the past, but for new GPSers there doesn't appear to be a need for the PC. i was also able to update my i5 to the latest software version without using the PC.
i know i still have issues for my Garmin CSx as it relates to GeoCaching, but the basic maps and updates are working just swell on a Mac. hooray!
EDIT: i see that this was already mentioned in the post just above mine -- i should have hit refresh. heh.