I was asked to set up a SQL Server 2008 cluster on Windows 2008 R2 this past week. One interesting issue I ran into was that only SQL 2008 SP1 is supported on Win 2008 RW. In that past, that meant that you could just do the SQL cluster install and then apply the service pack. Unfortunately, that won't work this time.
You must first create "slipstream" install media and install from there. It's really not difficult, mostly just copying files, but I was a bit nervous about it. Luckily, it went OK, and I now have my first SQL Server 2008 cluster in place and ready for production.