I have used it while lane sharing in rush hour traffic but you just have to be careful. If you position it wrong when you grab some brake it will cause you to open up the throttle more and usually abruptly.
Even when I use it I find myself not using it properly. I still have my fingers wrapped around the throttle pretty good and have to tell myself to relax.
I bought mine for 5 bux I think, so you might just get one and give it a try and find out for yourself.