I filter but not to the point of recklessness (IMO). I just don't do it at speed and have been looking ahead and planning multiple drop-out points. As others have said - its easier when you know the light sequence and how long each phase is so that you are less likely to be caught mid filtering when the lights change. And most motorists always seem to let me back into the queue (or I'm good at barging in regardless?).
I never criticise a cyclist who wouldn't do the same manoeuvre as myself as I have no idea of their skill level ... where as I know how fast I can accelerate or brake - that's not to say I never criticise myself - as I do make mistakes and hopefully learn from them.
If you watch drivers pull away from lights the gap between the vehicles tend to get larger, giving you a bit of space to drop into (with appropriate negotiation). I have to say that I very rarely filter except in a very long line of stationary traffic - but I am rarely in much of a hurry.
Stephen