Marathon is real, but do not be fouled, they are not sharp, they are very sharp! (I belive their odds department is better then that of Pinny's)
They offer best odds in the business, instant automatic payouts(after verification), but under average live chat.
Their limits are getting bigger the closer the start of the event is(as they received more and more volume). Their limits for each player are a result of their overall limit for a given outcome. It dosen't matter how you bet, they only care about math. For example, if they have an overall starting $100k limit for the outcome "TEAM A" to win(that limit is splited among all bettors), if they do not receive bets on the outcome "TEAM B" to win, once the $100k limit is hit, you end up with the limit of $1.3 for outcome "TEAM A" to win. In this case, you will find that the limit on "TEAM B" to win is very high and so on. The more "spreaded" volume there is for a given market, the bigger the limits they can offer are.
Although they have the best odds overall, on the long run, you will still end up losing money, thats how good their traders are. I belive they have insane odds calculating algorithms, since they still win money while giving you best odds in business.(or they have the "right connections")
I am with them for like 5 months now and their limits are slowly getting bigger and bigger as they atract more volume of play. I said "slowly"
It is my belief that they do not care how someone bets, they only care about what odds and limits they are offering. I think the odds they are offering are based on the probability of the given outcome and that the limits are imposed considering standard deviations and volume of betting for a given market.
As a man of science I can only respect their sharpness regarding the calculation of probabilities. As a bettor, I disrespect how they treat the support and communication aspects.