Cons:
Nine holes? Two nine holes courses? One 18 course? Zilker seems to have an identity problem and suffers from some false advertisement. Currently, a new to the course player can show up to expect 18 holes of golf with a definite distinction between each nine. Rumor mill is that the 18 pins are now going to be permanent, but take this information with a grain of salt, since it looks like it may be some time before the dust settles and people figure out the long term status.
Other major cons include no real tee markers showing the hole number or distance. The "South" course currently has yellow markers in the ground indicating the tee box, and the "North" course has the world's largest concrete pads to help to see where to throw. The north course has no numbers, so we jumped on a hole #2 (according to the map under links & files) near the road, since that made the most sense and the concrete tees line up well to show you your way. This way we could easily play 18 holes without backtracking to much because the north course hole #1 ends back at the parking lot where started the south course. The north course is also wide open, so you'll be able to scan the area easily.
The south course has some flow issues, so print the map, but note that you backtrack from hole #2 to hole #3, and take the left path through the trees after hole #4. Fortunately these pins have numbers, so it makes it harder to foul things up. Besides that - both nine hole courses are fairly straightforward with little challenge. Basically it's a good flat place to learn the game then have a dip in Barton Springs when you're finished.
Last issue is parking. Play on a week day or pay three bucks on the weekend? Believe me, unless you're hitting the springs as well, this course isn't worth three bucks. I second the other reviews that suggest you park under Mopac at the exit near course and walk across the frontage road. It's almost as close as any parking you would have to pay for anyway.
WORST HOLE/S: #6 North