According to a recent New York Times article they recon that age is going to play a key part in today's Pennsylvania primary. Demographically the state has a higher proportion of its population being of pensionable age, than most others. This is likely to favour Hillary who's core backers are those who are around the same age as her.
For me I find that it's a sad fact when people decide to vote for someone because of their age: because of their experience, avoiding those who perceivably don't have the right level of experience. It appears that they are backing Hillary and not Barack because she has more experience because of her age. The reverse is also apparently true, with younger voters generally backing Obama. I personally am not really bothered either way.
It will be interesting to see if this demographic analysis bares out in the final results.