Well here is my perspective of the Denali bus ride to Eielson Visitor Center and Wonder Lake :
I ventured on the Wonder Lake tour (rattling school bus ride) in July 1993 and back then it was a 12 hour scheduled trip with only a 15 minute stop before heading back....to me it was worth the long trip and that was because it happened to be a complete clear sunny day with no cloud obstructions of the entire mountain ranges.
I made reservations that were only two weeks in advance as that particular day was my three dayoff period in which I took the dayoff option rather than bump seniority as I had the option to still work, and back then they offered a $5 per person up to 4 people per reservation if you purchased only from the Fairbanks Visitor Center of which I done so.
However I will say this : If the weather is overcast, rainy or miserable, the trip to Wonder Lake is not worth it in my opinion.
In July 1998 I ventured on the more comfortable school bus ride with the thick cushioned seats minus the rattling noises to the Eielson Visitor Center in which they had a 45 minute stop if I remember right, which they added a few extra features in the visitor center from what they had in 1993 which was a substantial improvement, but it was thick overcast with hard intermittent rain and gusty wind periods that day and was so miserable.
I made reservations well in advance because of four extra family members visiting for that scheduled week, and back then the bus ride was something like $10 per person or $25 per family of four (to any destination tour you choose) if you purchased them only from the Fairbanks Visitor Center (as they were the only place that offered the best deal) as those deals are long gone now, unlike the park entrance fee plus the different rates to the different destinations they charge now.
With all that posted, if one does venture to Wonder Lake, it is such a looooong ride back good day or not, as the 20 or so miles between Eielson Visitor Center and Wonder Lake isn't all much to awe about.
Although I have not been to Denali Nat'l Park beyond Teklanika since 1998 (on bus tour), it's a bus ride I would not care to do more than once to a repeating destination but it is worth the experience for a first timer.
April was generally my favorite time to visit Denali Nat'l Park when they open the road to Teklanika at mile 31 as we used to go on a nice Sunday type of drive, before the park officially opens.
Good luck to all that go visit and hope you witness the clear days on the bus tour.