Pros:
Excellent course. Old Settler's is an extremely challenging course that is not for the faint of heart. The course is set up to play in a circle around a lake.
The park is really nice and is kept in good shape. There are signs on every hole and it is really easy to find the next tee box.
Hole #16 is the marquee hole. You tee off from on top of the dam and have to clear a corner of the lake in order to get to the pin.
Cons:
This course is LONG. I mean it. There are two holes that are 1000ft+. Aside from a couple of holes in the trees, most of the holes will test your arm.
For some reason, Old Settlers is really windy. If there is any wind above 10-15 mph in Round Rock, you may want to think twice about going because it will likely be 25 mph at Old Settlers.
Also, there always seem to be people using the park and the lake. If you go on the weekend, watch out for bystanders.
Other Thoughts:
Many Austin players have never bothered to drive up to Round Rock to give this course a shot which is a real shame. Old Settlers is an awesome course.