It sounds like these instruments had a lot of time and engineering go into them. If GH:WT's aren't as good I'll be very motivated to buy the full package for RB2 and then buy the stand a lone game of GH:WT assuming these new instruments are compatible with GH (notice how Activision/Neversoft reps said that RB instruments would work with the new GH, but that doesn't mean RB2's will).

Games don't progress linearly in graphic quality as time goes on. This has 360 quality visuals, but I think people expected better than Gears or something and that's setting yourself up for disappointment. The biggest upgrade is definitely the water though.