Spock's behavior in WNMHGB (or was it The Cage?) was so different than later Spock that it's easy to assume he just matured some in-between. Less shouty*, more confident, not trying so hard. That gives Quinto plenty of space to make the role his own without upsetting the canonistas (any more than they will insist on being upset).
*Not that I want QUINTO'S SPOCK TO BE CONSTANTLY SHOUTING!!!!
Moving on to Sylar...
Quinto feels that there is a chance to redeem Sylar, that he isn't all bad. "It depends on what his motivation is," said Quinto. "He has a lot of different reasons to do things this year. They don't all originate from himself. He's being put into situations where he has to do stuff for other people."
A lot of Heroes
fans want Sylar to diediediediedie, but I never figured that would happen before Trek XI
comes out. Kring will want to use the publicity to help Heroes
(the way the Nielsens are going, they can't get cocky). Sylar's survival hinges on the success of Trek XI
- if there are going to be more movies, Sylar is far more likely to live.
And for him not to be repetitive, he does need to be "redeemed" in some manner, though what that means and how it is plausibly accomplished remains an open question. The writing on the character has always been iffy; Quinto is really holding up far more than the actor's usual half in making a character work.