I just played for about two hours this morning after it finished downloading (I'm getting it as soon as GS here gets it, calm down everyone

)
I have to say I'm liking the song selection more than at least the US versions of DDR, and I'd almost compare it to the JP versions. I guess I'm a sucker for "cheesy techno" and "eurotrash." It should be noted that there are a couple of tracks from E-Rotic included (they did some stuff for the earlier DDR mixes)
I also really like the new elements (hands and minds). They take a bit of getting used to, but somehow they seem like they fit right in, and add a bit of fun to it.
My only real big complaint would be the loading times. Yes, I know load times are just a harsh reality, but it seems kind of strange to have such long (and so many for that matter) load times, when DDR has almost none.
As far as the reviews go, I already covered the music selection, but for difficulty, I'd say its nto much more than DDR. There is ONE song that is higher than 10 on hard (Pandemonium, 11). The "hardcore" stuff isn't there until expert. I havn't personally played Medium or lower, but I've heard that Easy is almost too easy. That said, I really wouldn't see much of a problem for casual/new players.
So I guess overall, I'd have to say this:
It's DDR, but only in the sense of the gameplay mechanics. The music is quite different, with much less pop/J-pop, and a lot more straight up techno. The extra elements (which aren't really included until Hard/Expert) are, I'd say, a refreshing change, since nothing's been changed in DDR since 6th Mix. For most DDR fans, I'd say get it, but if you're unsure about the song selection or anything else, try it first.
EDIT: I forgot to cover the cheese factor. I'd actually say that the music in ITG is quite a bit LESS cheesy than DDR, contrary to the reviews I've read.