BAs don't really need to be burned in (I'm undecided on dynamics). The bass may not be what you expected, but it is there in spades and it is high quality. You may need to adjust your expectations, possibly redefining what is good bass vs. loud or accentuated bass. I have many tracks that can produce very low rumbles from these, and they hold it together.
I enjoy my TFPs, and as I said, they remain competitive today. Even the Shure 500/530, designed and released around the same time, is competitive. At these levels, it really depends on the sound signature you are looking for.
I have become more interested in dynamics over the past two years, possibly because of their improved quality, and possibly because they don't require a crossover which may affect the signal phase. The better dynamics (Sennheiser, Monster) sound more cohesive to me, and the bass extends a bit deeper than most of my BAs (admittedly not of recent vintage). That said, the TFPs also possess a treble extension that is incredibly unique and airy, and go as low, but maybe not as loud, as my dynamics. As I noted, at this level, they are all very good, but do things differently. It depends on your preferences.
Hope this helps.
Edited by Dobber65 - 5/20/11 at 1:23pm