Has it been said that the GHWT guitar will not work with GH3? If it has, I am unaware of that. Regarding DLC vs. disks, I suppose that's a case of different strokes for different folks. Personally, I prefer having the songs on disk so it doesn't eat away at my hard drive space (as well as being more portable). I guess I never considered putting in disk one instead of disk two to be such a huge hassle, but I get what you are saying.
Yes. GHWT uses drums, mic and a new guitar with a touchpad. The music from older versions of GH will not be compatible. There is no song conversion built into the new GHWT game so that you can use your old song content. So any songs you liked on your older version will have to be purchased again if you want to play it on the new game.
Here is one article quote.
"World Tour would not be backwards compatible with
Guitar Hero III DLC."
http://www.1up.com/do/newsStory?cId=3168347
It was mentioned in more detail in another article. I will find it.
Somehow Harmonix figured out away to include backwards compatibility. I bet the first time it loads on your system it updates your downloaded song library and converts the files so it can be used on old or new instruments. Just my guess because I seriously doubt it does it on the fly. So if there is a menu to pick your instrument version, the music files still have to be compatible with our selection. So, it must update something for Rock Band 2.
I wish GHWT would have done that as well. I have to be honest, I really like a couple features like the drums being able to play notes either loud or soft depending on how hard you hit it. Also, the song creator sounds pretty cool. Not to mention the drum kit overall seems pretty cool. I will wait though for a full detail of what Rock Band 2 has and what instruments changes they have made etc. before making my final decision. I just think keeping my current library of songs through successive versions of Rock Band is going to be hard to pass up on.