I've signed up for a Tastyworks account and have a small balance there trading alongside IB. I did this because their commissions are 1/3 cheaper (.10 vs. .15) on IB, which can make a large difference.
Their software is not as intuitive as IB or TOS, but it's not hard to use.
Yesterday, I was stunned because I was consistently getting better fills on TW than IB. For instance, on the BUD trade:
1. I entered my order on IB;
2. I then entered by order on TW at a LOWER price (by .02);
3. The TW order filled, the IB did not.
This happened to me on BUD, JD, and HPQ. I could not get a full position in HPQ on either platform. I was ready to permanently write off IB.
Today has been a little different, as they have each performed almost identically. When I was re-entering BUD, I immediately got a handful of contracts on IB filled, then entered by order on TW at a better price, but got no fills. When I moved it to match the IB price, I also did not get any fills. Over the next 20 minutes or so, I bumped the price up a .01 or .02 - they'd each give me partial fills at the same price. So today, I'd say performance was about even on fills.
I'm going to track this for about a month.
And yes, it's a pain to trade two platforms.