FYI, for those who haven't seen this already:
I saw a sign last time I was there stating that your comp balance can be redeemed for Bonus Play at a ratio of 3:1, that is, $300 in comps can be converted to $100 in Bonus Play.
Also, Greektown will be running some Blackjack tournaments with a $100 entry fee, which can be purchased with $200 in comps. My abacus isn't handy but this looks like something in the neighborhood of 2:1.