I know that MarketWatch is often thought to be one of the best sites out there. But I can't say enough about how unhappy I am with their customer service.
After working with Questrade for the past 3 months, I can say that my experience has been positive, but I can only give them a three-star rating for the time being.
Low-cost, high-performance. To be honest, the compliance/etc. systems are all robots, so they're not the easiest to work with, especially if you run into problems. For seasoned investors, this is the most important piece of advice. Those who are just starting out should avoid it.
Customer service is really good. They are very helpful. App and website are both great, but I think the app is even better than the website I've told a lot of people about it.