I've bought and sold a little on Bittrex and, whilst I haven't had any bad experience with wallets being frozen, I'm not a big fan of the interface itself (a subjective view obviously) . They have a wealth of different trading pairs on there, but the UI and order types leave a little to be desired. They don't offer FIAT pairs either, although they have recently added the ability to see values in USD amounts, which is a step forwards.

My exchange of choice at the moment is Kraken. Fewer trading pairs, but they include USD, EUR, GBP and a couple of other fiats. The Cryptowatch graphs are as detailed as you could ask for and you can include MACD, RSI, and other toys to make it look like you know what's happening :) Their default charts are rubbish, but the Cryptowatch ones are good, if buried away a little on the site.

Good options for trading orders too, including conditional orders. Maybe give it a look and see what you think, although I think verification times on most of the exchanges at the moment are pretty long.