Re: silar question - spoilers
The $64000 question indeed.
The key to silar and the way in wich he accesses his powers is his back story.
We discover he's a watchmaker by trade, but more importantly his passion is for looking and working out how a mechanisim works. So we extend this logic forward to his power - for him to "absorb" a power his mind dictates he needs to understand the working of the machine - and in this case its the brain of the machiene hence why he takes the brain out - note here that all you ever see is the brain being removed - theres no other piece of info such as he eats it or something else - he simply "removes" it. We can therefor extrapolate this is akin to him taking the brain out and examining it somehow in the same way he examins a watch - and once he understands how the mechanisim works he can then access that power.
Peter if you look at his absorbing power is not to dissimilar. he only learned how to fly becuase of his strong emotional bond to his brother.. next after being tought to access poewrs he does this by "thinking2 about that person who had those powers... he's therefor in his own way examining the mechanisim but becuase he was a paliative care nurse his mind is more intune with the person... he emotionally connects to humans and thus is able to access those powers.
Personally I think Silar and perter have exactly the same power but becuase they access the world in a different way - silar looks for mechanics, peter looks for the human connection they absorb and therefor access their power in a different manner - however most importantly they BOTH "absorb" and could both do it in the same way if they thought the same way.
as for Peter being able to withstand the frozen time field this can be easily explained - the first time he meets Hiro its an intentional meeting - Hiro is controling the time bubble... ok we know peter absorbs powers so in later episodes is "immunity" to time fields could be explained by peter subconciously activating that power (even though he dosent understand how to fully use it) to break out of the time bubble.
Silar - well this one is a little more difficult but again we know he eventually kills her to get her power, yet seemingly resists her first... this for me was the key event (though could have just been sloppy writing) as its shows he is able to absorb in the same way as peter (even though he didnt realise it at the time) and therefor be "immune" to the effect prior to killing her.