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I have only stayed within walking distance once. I had a miserable experience and I won't do it again. Every other time I rented a car and stayed farther away.
Of course, the room costs are cheaper and there are usually plenty of choices. There are plenty of places to eat in the city and since you're out of the immediate convention area, are typically not crowded.
I don't mind to walk a few blocks so parking is pretty inexpensive for me as well.
In the end, it depends on the experience you want to have and what your priorities are.
The drive in isn't bad. FWIW, I live in Indy and work downtown, so I have parking, and have been doing the commute for over 2 decades.
The buggaboo is that all the extra GenCon people will be bunging up the traffic downtown.