You can hover your mouse over a player from your friends list, in the Game Screen, when inviting to check their stats.
This works 70% of the time, the other 30% no pop up of stats appear at all.
at the moment 'mouse hover pop up', cant be done outside of the game window - on your friends list - you do need to click the friend and open their profile.
for those who arent on your friends list and join a Game Lobby, you wont see their stats at all until they are in the game.