No backward it's such a bullsh!t. At least for the first year, it needs desperately of backward, the library will never be so compelling.
To be fair my views on B/C have changed recently.
I don't think it makes or breaks a platform at all. After all the PS3 library won't sell a PS4 to PS3 users OR non-PS3 users. Either way its not PS4 games.
Whilst they can offer PS3 games over download.
The only issue is not wanting multiple systems under one unit. Which I don't think doesn't play a part in a buyers decision BUT again; you won't get a PS4 unless you want the games, at which point buying a 720 and WiiU have the
same issue; two systems instead of one.
Certainly B/C should never be used where it might raise the price of the system too far.
I think its nice - but ultimately for the 720/PS4's of this world its a price that is in no way worth paying.