The core setup for a 2014 server isn't going to be any different than for a 2008 server. After that, it completely depends on if you're using functionality that wasn't present in 2008 such as Availability Groups, Columnstore indexes, In-Memory OLTP, etc.

There is one principal difference that's going to be noticeable to everyone. 2014 introduces a new cardinality estimator within the query optimizer and statistics generator. That's going to possibly result in lots of changes in behavior to lots of queries. You can turn it off by leaving your databases in 2012 or earlier compatibility mode, but then you can' use any of the other 2014 features.

As to what's new, it's in the documentation.