I've ridden across several times. Some of my experiences are below:
The Casino in Boonville is ok. You can't beat the convenience. I don't like the smoke. They've changed the rules in the past few months to actually allow you to take your bike to the room. The Frederick is nice, but pretty expensive in my opinion. The Comfort Inn out by the highway is not one of the better Comfort Inn's I've stayed in and is hassle to ride out to.

The Globe. Jeanette is SUPER nice and quite inexpensive, but I won't stay there again simply because I DO NOT LIKE CATS and she has several of them.

Amanda at the Dollhouse in Rhineland is a very, very helpful hostess. Not the cheapest place to stay, but nice. The food across the street at the Trailside Bar and Grill has gone downhill bad in my opinion over the last couple years. I thought it used to be a lot better.

McKittrick is fine. I like Hermann with a variety of meal choices. I have stayed at the Vinchester a couple times and that has worked fine with me. Very basic-but clean-hotel room but the price was very pretty inexpensive FOR HERMANN. Especially true if you're not trying to stay during festival weekends. My recommendation is to stay away from Hermann all together if its a festival weekend.
Lococo House in St. Charles has been good to me in terms of shuttle service etc. That said - I prefer hotels to B&Bs so have used several good options in downtown St. Charles.
Hope this helps. It is JUST ONE OPINION. Take it as that. Have a great trip!

Thank you for all the info!