Mag Creek is private as well, but both those courses as well as Bay Oaks in Clear Lake (which isnt too far) are both under Club Corp, so the awesome thing about it is that if you do join you should get playing privileges at those as well as a number of other Houston area clubs for just a cart fee (depending on your membership plan of course). If I didnt live in Pearland I would have went with them when I was looking for a club, but Golfcrest was half the distance and I got a great deal there.
I have played South Shore, and I like the 3 nine hole layout for variety, but I dont consider it anything spectacular.