From other stuff i've read, there is still tuning in the game - just not the in-depth stuff, and the handling is also customisable from arcade-esque to full sim. Interview with some guys from the dev says it uses exactly the same physics engine as forza too so calm down chaps. I think the point is that they're trying to target the people with this who don't traditionally enjoy the full Forza series, i'm sure there'll be a full version out next.
Where i think they maybe missed a trick is a garage import option from Forza 4 - surely could have been integrated?
As much as i love the cars, tuning & tinkering of forza, i find the career mode decidedly lacklustre so i'm interested to see what this can bring to the table in that sense. It may not be as photogenic but that doesn't necessarily make it a bad game.