Let me start by saying the experience itself was lots of fun. You get get drive fairly new Jeep Wranglers through some beautiful country, with interesting narration provided by the guide over CB radios.
The two major disappointments were the route and the pre-trip bus ride.
We were under the impression that this trip was actually *into* Denali National Park - when it is actually about an hour's drive out on Denali National Highway, and back. This is not the fault of the tour - I'm sure they said this somewhere, we were just disappointed, that we could have basically done the trip ourselves (as it is all on public roads) just without the guided narration from the tour operator.
Secondly, the tour group provides a great service by picking up passengers directly from multiple lodges in the area, which is great unless you get motion sickness. Some of the winding drives are a bit nauseating, and since you're on a 20 passenger bus, there are no seat belts, and it's a bit of a jostling ride.
In the end, if you are comfortable driving on dirt roads, and don't feel like you need an audio track to walk you through what you are seeing - you could probably get by with driving on the Denali National Highway by yourself and save a few hundred bucks.
However, if you know what you're signing up for - and your rental car isn't 4WD, it's a fun trip, in a heavy duty Jeep and you'll see some amazing scenery on the trip.