I applied to the 2+2 program also. You're right, it will be interesting to see how this whole thing works out. From what I have read, HBS wants to eventually admit 10% of their class through 2+2 (so that would be ~90 students). But they've also said that this is a goal, and they will gradually get there. They've also said that for this year (the first year), they will just let the strength of the applicant pool determine how many students get admitted through 2+2. So for all we know, they could decide to only let in 5 students through 2+2 this year...
My credentials:
GMAT - 740
GPA - 3.99
Double major - Mechanical engineering and mathematics
P/T Work experience - mechanical design at a defense contractor, research assistant at school
I also took 2 years off of school between my freshman and sophomore years to volunteer full-time as a missionary for my church.
Personally, I think it's hard to say what your chances are, because no one really knows what HBS is looking for through 2+2, as this is the first year it's ever been offered. Sure, HBS has said a few things about it, but there aren't any past results to go by.
Good luck though!