Welcome back!
There aren't too many changes, the game for the most part plays the same. The biggest changes, I would say, for good or for bad (I have ranted about the merit's of the changes elsewhere on the forums) are minimal. Some of the more noticeable changes include:
-More heroic actions on which to spend might.
-A few new spells. Nothing game shattering, unless your are a spirit
-Weapon special abilities (gone are the days of the big blue rule book's statement of, "a hand weapon is just a hand weapon whether it is a sword or an axe." There is a big difference now).
-Elven blades got a well needed, yet minor and well thought out, boost (especially with the warbands rule of all characters carry hand weapons unless noted otherwise in their profile).
-Monster boost. Monster's got a huge boost. I still think it was too much. However, I admit that it brought monsters into a truly terrifying realm and, frankly, monsters needed something. However, I personally think they got too much. But that is me and I seem to be alone in my opinion. /steps off soap box.
If you have been out for 10 years you probably need an explanation of warbands too. In a nutshell, you can no longer field gil-galad and 100 elven warriors, or a horde of 200 goblin warriors. Your army is made up of a number of warbands. Each warband must possess a hero, and each hero may be supported by up to 12 warriors. Normal archery rules still apply 33% (however, there are exceptions to the bow limit now as well. Certain armies can have up to 50% bows and some legendary forces can possess a 100% bow limit meaning everyone has a bow! Heroes do not count against your bow limit). Your army may contain as many heroes/warriors as you wish provided you do not exceed your agreed upon point total. In sum, most forces include roughly 3 warbands (so three heroes) with up to 36 warriors (up to 12 for each warband) depending on how you spend your points. Yes, you may have a warband made up of a single hero with 0 warriors. No, you may not have a lone warrior by himself with no Hero to follow.
I've been playing for 6 years (almost 7) now so I can only speak for the previous six years. The first four years you were out, you'll have to consult a more veteran chap than I. I am, however, one of the more knowledgeable chaps on the forum. Just kidding, in all honesty I am probably one of the more bothersome chaps as I am always requesting rule page citations in addition to posting rules question clarifications. What can I say, the scientist in me doesn't take much at face value. You have to back it up with evidence, and then I challenge your "evidence" or lack thereof. Now that I think about it, I am probably viewed as one of the more annoying members
. I can write a killer story though, just search Unsung Heroes with the forum's search function at the top.