Zoolights is a wonderfully unique Phoenix experience for the holidays and is not to be missed. There is a growing light display each year, some kiddie rides (jumpers, sleds, camel rides, etc), plus a few nocturnal animals to view sprinkled around. This is a wholesome, active and fun way to spend an hour or two with the entire family. It is quickly becoming a Christmas tradition for /this/ family... Unfortunately, it looks like this is the case for many other people across the Valley. The place is packed!
The main negative points are that a massive number of visitors combined with narrow, dark pathways can frustrate anyone with a time limit or claustrophobic issues. I'd say there is also room for improvement for the variety in concessions. But these are minor annoyances. Overall, you will not be disappointed.