What Rob said - the songs on ADTOE are only as similar to IAW as one human is similar to another human - there may be all the same limbs and organs and body parts, but the composition itself is different.
As for the similarities that exist, either in form or structure, I think they're neat, and it really only enhances a great album even more. For being an album with a new line-up, it's definitely right up there for me. Then again, albums with new line-ups tend to have a lot of great songs - IAW, FII, SFAM, and now ADTOE. Great music, great production, and an over-all sense of "here's all we've got!", but not really in the sense that they've got to go out and prove themselves again with ADTOE, but because they want to reassure us that they are still DT.
On a related note, the 2nd album by a "new" line-up produced some even GREATER (albeit more fan-splitting) albums: Awake and SDOIT. So I wonder if DT12 will become as polarizing as those albums have become in the fanbase?
-Marc.