The Round Rock Outlet has a nice circular layout with the majority of it being covered (which was very helpful when we visited since it was raining on and off). It is part of the Premium Outlets, which in my opinion, usually attract better stores (although the prices are not always "outlet" prices). The Round Rock location had the usual stores, not really anything special, but it was enjoyable to shop mainly due to its layout. It was easy to hit the stores that we wanted to (Nautica, New York & Company, Reebok, Fossil, Van Heusen, Izod, and a few others) quickly and get back on the road.
A recommendation: Before going, be sure to log onto the website and print off coupons and a voucher for a free coupon book.