My two cents (having owned the TF10s and now owning the IE8s): I thought the TF10s had wonderful bass and very good treble (although that's my least concerned part of the sound spectrum). But to my ears, the TF10s midrange sucked BIG TIME! I love bass and I love midrange, so the TF10s didn't work out for me in that respect. Vocals through the TF10 sounded very unnatural and lacked the nuances I was use to getting from other earphones I had (before purchasing the IE8) such as the E-Q7, IE7 and HF5.
Ironically, to my surprise, the TF10s did pretty good with jazz (despite of what I just said above). But it was jazz without vocals. I listen to a lot Brazilian jazz with acoustic guitar, and the TF10s tended to shine for some reason, but the music still was heavy in the bass and treble range. In the end, although I didn't hate the TF10s (except it's midrange especially for vocals), I just decided it wasn't my cup of tea.
Only owned the IE8s for about a week, and even with the strong bass presence, the midrange still pushes forward for me. The treble seems a tad bit recessed, but that's fine for me. On certain tracks, however, the treble really shines. I am a basshead, and whereas tuning up the bass doesn't bother me, I've found I enjoy the IE8s with the bass port on the lowest - number 1. I get plenty of bass and the other sound spectrums perform wonderfully.
I was not expecting, to be honest, to like the IE8s as well as I do. As I mentioned above, I own the IE7s and like them a lot, but the music is a bit too colored for my taste. I was expecting that coloration with the IE8s, but have found it less so than with the IE7s. In the end, however, it's the soundstage of the IE8s (much wider than the huge stage on the E-Q7s and IE7s) that has made me love these phones in a short period. The soundstage, I believe, allows me to hear details in the instruments and vocals that I haven't heard in any dynamic earphone I own - armature except for the E-Q7. The E-Q7 is still my favorite IEM, but the IE8 is almost equal to it for me. They don't sound just alike, but each offers a little something that the other one doesn't that complements each other. So they are my two top earphones (one in the armature category, and one in the dynamic category). Wish I could stop, but am always seeking something that can top those two. I haven't heard one yet, but I'm sure it's being built somewhere.