The bike should be perfectly fine for 100 mile ride, specs look similar to other products in this price range. I'd rather bother myself with fit and comfort, these will mean more on long distance ride, ask LBS for a test ride.
> doesnt have disc brakes, is this a big deal?
If you are not going to descend mountains or ride in very wet conditions, then no. People are riding without disc brakes for years, it's just another option.
> sora gears set seem to be well reviewed
Sora should do the shifting alright.
> carbon fork keeps this bike light?
Not exactly, aluminium forks are about 200 grams heavier than carbon fiber, which isn't big deal, given the bike weight almost 10kg. It should be somewhat more comfortable, though.