This is a must see! I drove through around sunset, and it was a great time of day to be there. The architecture is absolutely awe-inspiring!
I highly recommend listening to the Jurassic Park episode of the Criminal podcast as you drive through the park. It covers the history of petrified wood theft at the park, and how the park has responded. It was a very interesting podcast and it enhanced the experience.
The drive through portion of the park is amazing! I would highly recommend taking the time to hike the Blue Mesa Trail. It's absolutely gorgeous, and pretty short (around 1.5 miles). Don't listen to reviews saying that there is hardly any petrified wood in the park. These people clearly don't know how to identify petrified wood! It really is everywhere in the park- especially along the trails.