Hmm, I appreciate those voting, but not much discussion! Here's my (admittedly limited) experience:
1. Which deck to pick each series? For Series 1, I think the Aragorn Deck is clearly superior to the Theoden deck. The Theoden deck just seems generally weak to me. For Series 2, I think the Legolas Deck is the better choice (particularly if you went with Aragorn in Series 1). I myself picked the Eowyn Deck in Series 2, and immediately regretted my decision as soon as I started playing with it. I think the Legolas Deck really adds the advantage of archery and usable powerups. It also offers support cards for your 2x
Southron Commander, which can be key to either knocking a large fellowship down to size, or overwhelming a Frodo with a
Hobbit Sword and/or
Severed His Bonds. For Series 3, I think the Witch-king Deck is the smartest choice, primarily because of
Orc Insurgent. I myself went with the Faramir Deck this Series, and while it wasn't bad, I suspect the Witch-king starter may have been a stronger choice.
2. What's different about the Gemp versions? Well, as far as what I've noticed, the only thing different is that both starters in Series 1 come with 2x
Southron Commander. I think that's the only difference, but I"m not positive.
3. Strategies? Obviously a lot of this is going to be dependent upon what cards you pull. I was lucky enough to get a
Constantly Threatening, so it was a pretty obvious strategy to build the deck around. I feel like I did better going second, but then my fellowship was relatively weak and could not move very quickly. I think strategy generally needs to be kept pretty simple for Sealed, you won't be able to swing a bunch of fancy card combos. One thing that did work well for me: I got a few of those Uruks that prevent hobbits from being discarded. In conjunction with
Southron Commander, this generally means I can force a large fellowship to discard some guys that really count, rather than those pesky hobbits. It seems like winning a game in Sealed normally comes down to swarm, which generally means dropping some kind of bomb on them fairly late in the game. So you want to maintain good cycling, keep your fellowship alive, but primarily build up the perfect hand to bomb your opponent with.
That's my advice! But then, I'm currently ranked 49th!

Anyone else?