I did mine with friends years ago and it was probably the single best home improvement I made.
Very straightforward to do but spend some time designing your zones. I wish I had spent more time on that. Keep in mind any hanging baskets or flower beds that you would want to water and I would suggest putting the "flowers" on a different zone so you can water them more often for less time.
Orbit
http://www.orbitonline.com/ has an online system designer on its site.
Like Rathji said if you are going 90% of the way, go all the way. The extra cost is made up in time in about a week.