I recently had the pleasure of staying at the JW Marriott Indianapolis when traveling on business, and it did not disappoint. The staff was very friendly, the room was clean, and the location was a quick cab ride away from my client site and the airport.
The restaurant was a bit overpriced, however, and the food was just okay. No refrigerators in the room if you wanted to store leftovers. Also, while the room was clean (and certainly up to my standards) I did notice the clock next to the bed was incredibly dusty - but this was really only noticeable at night.
A pleasant surprise was the minor league baseball stadium that I could see from my hotel room. Fun working during the day from the room and hearing the roar of the crowd.
Overall a positive experience - and probably the best place to stay in Indy.