A big plot problem I've had with this season is what they've done with the eclipses. It's a random deus ex machina that doesn't even fit in with what they've done in past seasons. Remember, their was an eclipse when Hiro jumped back to feudal Japan in season 2. By all rights, he should've lost his power then. Also, how exactly would Adam Monroe survive if he were over 300 years old when an eclipse occurred? He would've been withered away to dust long before 2007.
I still love the show, and I'm still going to watch regularly, but this plot point is really too glaring to overlook.