I have to agree with Steve here. We are managing literally hundreds of SQL Server 2005 instances in this environment. With 6 cumulative updates since SP2, its next to impossible to manage that across all of these environments.
In addition, when we build out our "gold" build for SQL Server in our lab, we prefer to install the latest service pack for testing. Now, I suppose you could install SP2 then the cumulative update 6, however its just easier to have a single service pack to install that covers the whole thing.
However if its an issue of timing and resources on the Microsoft side, with the SQL team busily working on SQL2008, I don't want them to rush a SP to market because the community is jumping up and down for one. The worst thing that could happen is that SP3 isn't properly tested, and contains a bunch of issues that could bite you in the rear end.