I've been day trading for a bit over a year and used my sim trading account with IB for the first time this week. I used it for 2 days to practice trading ES (which is very new to me), trading an opening range strategy that I've been hesitant to trade live.
I used the sim account to get a feel for entering quickly on signal, putting in a stop quickly, and managing the trade. I found it useful in the "look and feel" arena (it definitely beat paper trading where I jot down my entry and exit prices and check the chart to see stop was hit).
Sim helped me react faster, because with no real money is on the line, I had no problem immediately putting on a trade that set up without running through 5 different analyses of the setup in my mind.
After trading ES with the sim account, then switching right over to my main PC to put on a live stock trade, I was quick, getting a nice entry price, instead of hesitating as I sometimes do.
Then the next day I traded my opening range ES strategy live and took the signal quickly, twice, first time stop loss hit, second time right back in for the real move.
So in that regard it turned out to be very helpful.
I also used it to trade a high-priced stock I never traded before that had a wide spread. Sim helped me "get to know" this stock and how best to trade around that spread without getting stopped out.
I think it's useful to compare how you trade sim vs live and correct any discrepancies that hinder your live trading. I found that trading live, I moved my stop too quickly to lock in profit and ended up leaving quite a bit of profit on the table. I'm sure if it was sim I would've been more patient and let the stop sit at break even for a while.
So I may sim trade occasionally to practice improving my reaction time and to practice patience with trade management, but as another poster here said, even trading 100 shares live will beat sim for testing your ability to follow your rules and keep emotions out of trading.
(Except when a trade goes quickly and hugely in your favor. Seasoned veteran trader Robert Weinstein taught me the appropriate professional reaction a trader may use in that situation: "Yippie!")
