Pretty much just to echo what other people have said already...from a financial perspective pretty much all of these services will lose you money. They are for people who don't do the calculations. I mean when you first hear "$10 for 1GH/s for a year" it sounds pretty good, but when you add in their maintenance fees and realize that BTC difficulty is only going to keep jumping up then you still won't break even in the end. If you are betting on the price of BTC skyrocketing then you should just buy BTC instead. That way you at least know exactly how much BTC you will get for your money instead of just an estimate based off of hash rate and predicted difficulty.