Jeff is correct, and this is one reason I recommended against them. They weren't as thoroughly tested, and there was legal wording added to the documents noting that if you didn't experience the issue, you ought to wait for the next SP.

The CUs now receive extensive testing. I'm not sure SPs get more these days, especially the last few. That doesn't mean they're perfect or they don't need more tests, but I think they are as heavily examined as any patches the SQL Server team builds.