Marble Falls is great. I lived their for a brief period and a friend of mine has a house in Granite Shoals. If you can get on the water, the lake is great. They say LBJ is the only true constant level lake in Texas, making it very desirable from a home perspective.
Granite Shoals is a bit dumpy, like any little lake town, but once you get to the lake properties they are generally really nice homes.
As C-Jags mentioned, over on the other side of the lake is Horseshoe Bay and the homes around there are very high end. The hotel resort there is still very nice I believe.
You're also only 25 minutes or so from Bee Cave. Longhorn Cavern and Inks Lake (my favorite lake of the Highland Lakes) State Park and Perdenales Falls State Park are nearby.
Marble Falls also has a nice downtown and good community events happening. I kind of view Burnet/Marble Falls as the gateway to the Hill Country.
Great place to spend some time on a vacation.