I've had good experiences so far with " Coinex " and " Cryptsy " have added coins, gotten payouts on coins to my wallet or another exchange, an coinex has mining pools for those who jump around to most valuable coin to trade with.
Not sure about the others, I do know Mt Gox raised flags since it's almost always having the highest bitcoin value of all exchanges, that's just a red flag to stay away, any site that needs to promote via false inflated values needs to be avoided like the plague.
As for scams,
Gambling as from what I've seen is more set up than vegas, in other words you'd be more profitable playing the state lottery every day, pick 5 or pick 3 n 4 mid days, there is always Keno.
Just remember, TRUST NO ONE. It isn't the X files, but has just as many creeps.
