As a longtime fan of both Flash Tracer, the Firefox Flash tracing extension, and Firebug, arguably the best free web development extension available, I was ecstatic to hear that Alessandro Crugnola had created a FlashTracer plug-in for Firebug.
While it’s possible to have both individual Flash Tracer and Firebug extensions running at the same time, performance often suffers significantly. Adding Flash Tracer as a Firebug extension seems to have improved performance while making it more convenient and accessible.
As of this writing, it’s still in early beta but it’s working well enough for me. Check it out for yourself at sephiroth.it .