I was actually thinking of switching from thinkorswim, or at least adding another broker (IB or Tradestation)....
I have had issues with TOS's online version. They are rolling out alot of updates lately - which I think is great - but it sucks when they have an issue with their new version and I have to be the one to IM their tech support only to be told that I should roll back to the older version because they are having an error. Ex: one day the new version was unable to get quotes from several of the major exchanges...huge issue! Yet instead of posting a message with a solution, I had to call/IM and roll back to older version. If I was a more active trader, would be a gigantic issue.....
Another issue, one which I've been particularly pissed about, is when I close out a position, my buying power doesn't always return right away. (I would even go so far as to say that it almost NEVER does right away). I buy and sell alot of vertical spread - which require quite a bit of margin - and when my margin doesn't return right away after I close out, this really pisses me off, once again requiring a message to tech support.
What are your issues with IB? why do you want to change?