Just right. As far as guided tours go, the information was enough, but not overload. The time to explore after the tour was appropriate to check out whatever else interested you, but didn't leave you waiting to leave. Personally, I had free bus and heavily discounted train usage with my Eurail Pass and still felt that the transportation included tour along with a nice lunch was worth the value. St. Michel is a uniquely located Castle worth a day visit, but I personally would rather be back in Paris the same day as a opposed to spending the night there. I think this day trip is an excellent oppertunity to see this amazing setting without the hassle of trying do it all on your own or wasting 2-3 days of vaction wearing yourself out doing what this trips accomplishes in one at a lower stress level.
About me: young, adventurous, female, that typically travels solo with high level of itinerary flexiblility