Schiz, I'm using Google apps for domains and it really is worth some money.
$50 a user a year is a lot for free communities, but NOT for a company that no longer needs to update PCs with the latest M$ patches, or even pay the licensing fees on exchange server... IMHO their stuff provides 80% of the functionality at 20% of the cost. It's not exchange, but not everyone needs exchange ( 20% do?! :-) ).
Wedge, RE: integration Is your goal to use google authentication to enable/replace vanilla authentication?