Really really first impressions (with just 20 minutes - so take with a grain of salt):
- bass seems deeper than the GR07 (but this could just be because it has more of an audible mid-bass hump). bass is deep and not muddy.
- notes are thicker (as been stated by previous owners). the sound is more aggressive and more colored (again, as stated by earlier owners).
- nice clarity in the sound and that jvc trademark timbre. i'm really loving the timbre of the saxophone (clearly a winner over the gr07, and i like the horn instruments coming out of the vsonic, but there is no competition when hearing it from the fxt90 - and this before any type of burn-in. wow!)
- mids are are not recessed like they are in the fx700, and i'm really happy about that. gr07mids are more forward, however than the fxt90. at this point i like the gr07 mids a tad more, but that could change)
- treble is more forward and a bit harsher in the fxt90 than in the gr07, but i detact no sibilance yet.
- drums are quite nice, but i'm not quite ready to say that the drum are better than the gr07. drum are nice in both.
- vocals...vocals....seems like there is more clarity in the jvc's vocals, but the gr07 vocals are more forward and in front of the music. this is a toss up right now. both vocals are nice but presented differently.
- guitars are outstanding!!! i remember thinking the guitars were killer in the fx700, and i get the same chills with the fxt90.... guitars are also excellent with the gr07, but a flatter sound. i give the edge to the fxt90 (this is electric guitars...i haven't gotten to acoustic guitars or strings yet).
so very initial impressions is that these iems aren't hype up in being more than they are. it's a very exciting iem and already exceeds my expectations.