If it's Adobe Flash you're referring to... I can't think of any less optimal environment for real-time visualization. Flash/Ajax/buzzword of the moment will never replace the JVM in that regard.
Maybe I'm exaggerating... Flash has improved considerably since its early days of simple interactive web interfaces. Actionscript is OO-capable and Flash Media Server is pretty secure. I guess if the end-user is running a fast CPU with lots of memory, the difference is marginal. But I still think it's the wrong tool for the job. Sorry for the digression... I haven't come across a Flash-based trading platform, but I have seen AJAX used to update quotes in quasi real time.
I have not heard of any but if the end-user's cpu can handle it, I would not see any problems with it.