I have accounts with Fidelity and MB Trading, and will be closing my Fidelity accounts and maybe moving them to MB Trading. I have been with them for 2 or 3 years, and even though I am not a day trader I do like the system.
MB Navigator is a very nice trading platform, and the trades are fast and I seem to get a lot better price than when trading with Fidelity.
The commissions are awesome, and the reason why I gave this relative unknown a shot. It's $1.00 per trade per 100 shares with $4.95 max. With Fidelity it costs me $10.95 per trade, and that's their silver level. That's almost 11 small trades on MB Trading.
The price structure allows an investor to slowly build up a position without worrying too much about the cost of the commissions.
Downside is that MB Navigator is the only way I can trade, and it is application that must be installed on a PC. There is no web trading. Those with Linux, Mac or some other platform are out of luck.
One other major drawback to me is that MB Navigator does not display the cost basis. You get your positions and current bid/ask information, but if you are trying to make a decision of a profit/loss basis, than you'll have to keep track of that info yourself....or look through the "accounting" screens on the MB Trading website.

Also, if you wish to have mutual funds in your potfolio, MB Trading gets pricey - $50 per trade on no-loads.

Being one of the few direct-access traders among brokers gives MB Trading a definite advantage. The other plus is they provide their traders free software platform called MB Navigator that includes a number of customization features. One drawback though, it takes longer than a few minutes to download, but it does work.

MB Trading provides access to a wide variety of 3rd party trading tools including after hours trading. They also provide comprehensive tax accounting statements, and banking services through a clearing firm.

It's no coincidence that "Trading" is part of the name of this brokerage.