My wife, goddaughter and I took this trolley tour whilst travelling from Phoenix to Flagstaff. We took advantage of a Groupon deal that was easy to redeem via e-mail.
The tour is a bit of an oddity, in that it takes you through some of Sedona's practical features first (good restaurant on the left, art gallery on the right, etc.) before actually getting out of town and into the rock formations. I would actually recommend this as an orientation tour if you were staying in Sedona for more than a few days as it would give you an excellent overview of the town.
You didn't spend too much time in the canyon, but the transit to and from there offered some great views and the occasional vista. This isn't a particularly expensive tour and I think offers good value for money.