No problems whatsoever. I don't know of a single NPC group at OU where you're going to have a sub par experience. Yes, some of the houses are considered more selective. I have a cousin who is (if memory serves) a member of Gamma Phi Beta up there and my sister in law who graduated a few years ago is a Chi Omega.
Just be positive.
__________________ SN -SINCE 1869-
"EXCELLING WITH HONOR"
S N E T T
Mu Tau 5, Central Oklahoma