Question : move from 2008 to R2 (compared to 2008 from 2005)

How would you compare the move from 2008 to R2, compared to the move from 2005 to 2008.

Which is more complex and highly advanced move?
how impactful is it if the app is moved to the newer version?
any concerns or things to remember before upgrading version etc.
which is a smoother learning curve and which is steep?

thanks

Answer : move from 2008 to R2 (compared to 2008 from 2005)

R2 is 2008, so the move should be smoother. 2005 to 2008 was a big change with data types.

The only issue I ran into with R2 is this:
http://www.experts-exchange.com/Microsoft/Development/MS-SQL-Server/SQL_Server_2008/Q_26295554.html