David Portas (5/6/2010)
I think you didn't read the replies very well. A number of features were mentioned that are new to R2. Here's another link:http://msdn.microsoft.com/en-us/library/bb500435(SQL.105).aspx
I think that David's and Wayne's links are good places to start. Is there something you were using this for? Is there some business reason?
I see R2 as what it is, a 10.5 version of SQL 2008. There are improvements in areas, and new features, but in general, unless you specifically are using one of those, I'd skip the upgrade.