I have had accounts at both IB and Questrade. Whatever you've heard about Questrade, sadly much of it is true pertaining to 2007-2009. I have not had any issues with their service, and making the few trades I do with the QuestraderWEB service has been flawless. In the time that I've had the account, their service has constantly been improving (statements are easier to read, customer service is more responsive). You should read what FrugalTrader and Canadian Capitalist have to say along with the combined 1000+ comments before deciding.
Interactive Brokers is a whole different world. Those guys are the definition of real-time. You can get daily and weekly statements, along with the typical monthly statements. Buying power, margin, etc, is all updated in real-time and viewable in their TWS software. Trading fees are definitely lower than Questrade unless you're routinely trading 800-1000+ shares. Most of my trades cost $1. Options have a lower limit before Questrade makes more sense. And nothing beats IB for forex.
Ultimately it really depends on what you will be doing. Note that IB charges a minimum monthly fee of $10 ($3 if you're young and foolish). If you don't hit that with commissions, the balance is taken from your account. Also, all other fees are passed on to you (e.g. data, order cancellation). IB also doesn't have any registered accounts such as TFSA or RRSP, and doesn't plan to. If you'll be doing a bunch of hefty trading, IB offers a trading platform free of charge, but charges for everything else. Questrade instead has a monthly fee for its QuestraderPRO and QuestraderELITE services, but that includes data and flat rate commissions. If you're just looking for a place to invest cheaply without extra fees and plan on making a few trades a year, Questrade might be the right choice.