Thank you very much for this info. That's good to know. I guess the question becomes why are so many people talking about poor fills? I understand some people suggest it's because of an alterior motive, but could it be a difference with directly routed orders and orders that use their smart router? IB seem to really recommend their smart router over other routes. The person I spoke to said it also applied for market orders, which is the one of the key limitations of my current broker - they give me the absolute worst fills with huge delays on market orders, and I read a similar story for IB - admittedly this is for volatile small cap stocks (with volume though). I know it's never recommended to use market orders, but sometimes you have to, especially to get out. The whole point of the market order is speed to the end user - if I wanted to get the worst fills I'll just wait for the peak and bottom and send in my limit order.
Depends on what you call "so many people". If 1% of IB's customers are experiencing bad fills and talk about this publicly you would find 13,000 people complaining (IB has about 1.3 million customers). I doubt whether you find this amount of complainants.
IB has "protective" measures in place which slow down orders if they think you'd get a bad fill. I personally hate it as I want full control of orders. Many who complain also trade stocks with low volume. But of course there are times when IB's own systems are slow, it's rare but not unlikely. Just look at order acknowledgment speed right at the market open, there's considerable delay.
Because "so many people" use IB. When "so many people" use a broker, a lot of them will lose money and complain about poor fills when in fact they just made poor trades. The base rate take away is: Many people use IB. That fact alone speak volumes.
As others have pointed out, IB and TWS are one of the best. But if you want to get even better fills and less slippage (especially true for automated trading), running your software from a server that is either colocated with your broker/exchange, or at least located in the same city is important. Real colocation (same datacenter) is very expensive, and not applicable to most retail traders. But the next best thing is a reliable VPS provider in the same city. For example I use www.ninjamobiletrader.com because of their 1 ms Chicago servers, and I've seen a noticeable improvement in my system's performance.
1. Fidelity platform is God aweful for day trading, and not much better otherwise. 2. With Fidelity, 6-10 months back, I always got the best price and fill, but then things changed drastically 3-4 months ago. It may be a result of doing away with commissions and trying to make a profit. Before I completely stopped trading at Fidelity, the fill was taking 7-30 seconds, and I was losing money as a result. 3. I decided to use LightSpeed but never did. 4. IB was the best 10 years ago. I have had many problems, but still use IB for day trading. 5. I can't get their hotkeys to work, so I use "Chart Trader" with buttons with a stop attached. 6. Each button must be set for the shares. Why don't they have a place where you can quickly change shares for a chart, and then you wouldn't have to have so many programmed buttons??? 7. I used to use the Dom years ago, but I find that I always lose money when I use the Dom. The fills seem to be really poor on the Dom, whether Limit or Market, I always start off in the negative. 8. Using stops on the Chart is convenient, but the tiny hand is hard to grab the stop to move it.
Fidelity doesn't getting paid for order flow. Zero commission model doesn't work without payment for order flow. There is nothing wrong with getting paid for order flow. Executions are to 4 places + increased price improvement. Your conclusion about profit concerns resulting in in inferior execution is correct.