Wow! Interesting to see the reviews are all over the place. In an effort to avoid disappointment, I'll share my perspective of what Zoo Lights "is" and isn't:
Ticket Prices: If SRP is your utility company they offer one ticket free in the November billing. Paperless billing? It can be obtained from their website. You can also get discounted tickets on the Phoenix Zoo website. Just watch for the black-out dates. We ended up paying $10 per person since I forgot about the free ticket from SRP.
Entertainment Value: Think of Zoo Lights as a leisurely stroll through a museum. It isn't Disney. You won't ooh and aah, bowed over by fantastic sound, dancing waters, and fireworks display - though the lights in and surrounding the lake are choreographed to music, there's an animatronic giraffe, carousel, and camel ride. Parents it will be dark, so it's not a good time to let your kids run around.
Crowds: A weekday evening is the best time to visit - ample parking and since you will arrive with tickets in hand, you can proceed directly to the entry.
Concessions: Not crazy movie theater prices, but they will cost you.
Photographers: This might be the place to get that "special" shot.
All in all, me and my daughter had a nice time - a leisurely stroll, sitting lake-side for the light show, relaxing and chatting.
Hope this helps.
Merry Christmas and Happy New Year!!