''

Clarifications

http://www.microsoft.com/technet/prodtechnol/sql/2005/sqlupgrd.mspx
You'll have to wade through all the advertising bollocks at the top.

But the meat is in there

Step five of the post upgrade process, where you change the compatibility mode, is the bit that catches most out.

If you leave it on 80, you can get some real weird behaviour and errors messages when you start making use of the new features.

It's a very effective tool though, if you use it right.

.