Great question, I will try it out and get back to you.
One big thing to try out is if EPiServer works and how it performs in the great new feature In-Memory database that SQL 2014 has. I will try that out also
Just tried a Alloy MVC project with SQL 2014 Developer Edition and it is working great.
I have not tried in memory yet, since it takes a while to set up but most of the users will not use that anyway because it is a enterprise feature
EPiServer 7 does not officially supports SQL Server 2014:http://world.episerver.com/Documentation/Items/System-Requirements/System-Requirements---EPiServer-7/
My guess is that it still works, does anyone have experience with this?