If your plan is to migrate and then stop using Outlook, you need to move over your mail, contacts and calendars. It might involve some work, but at least it's only once. Personally, I do not like Entourage, not even 2008. It's slow and clunky and the interface does not really make me feel like I'm on a Mac.
There are numerous articles that can be found via Google on copying mail over from Outlook to either Entourage or Apple Mail, as well as copying your contacts.
Calendars: You can use Calgoo Connect (free), which runs on both Mac and Windows. You can install the appropriate version on each side, then sync your Outlook calendar(s) to a Google calendar. Once you are satisfied with the sync, do the same on the Mac side to sync the Google calendar with the Mac Address Book
As for MobileMe, it's is working great for me now, but with an iPhone in hand so if you do not have an iPhone you may not really care but... my iPhone is connected to my company's Exchange server and I use it for push e-mail and calendaring. For personal usage, I sync my contacts and calendars from my Contacts and iCal applications on OS X via MobileMe and then they get synced to my iPhone (via the cloud, not iTunes). For mail, I use only IMAP accounts (MobileMe and Gmail), so that I don't have to worry about keeping my iPhone and computer in sync.
I know that some users are still experiencing outages, but lately I've had no problems at all and it's working out to be a good solution for me.
Good luck, whatever solution you end up with.