E3 has revealed more on some of the characters skill trees, but I can't be bothered to throw up that info just yet.
I've been thinking more on some of the core gameplay changes/improvements in Borderlands 2.
-More enemies types.
-More weapon variety.
-More player to player character quips when in a party (a la Left 4 Dead)
-Improved enemy AI. More than just kamikaze and hang back types.
-Improved item cards. Item cards should now reveal all stats and bonuses. Some were hidden in BL1.
-Each weapon manufacturer will have their own unique build style for each weapon type.
-Eridium is now a rare currency. Used to either purchase top-flight weapons, or give temporary buffs to the player.
-Improved menu system. Skills, inventory, trading, etc.
It all sounds great, although it's the improved item cards that stand out. In the PC version of Borderlands the item cards could be modified to show up to six (maybe more?) lines of bonuses that came with any particular weapon or item. However, on the console version (for whatever reason) the item cards are limited to showing only four lines of item bonuses. So if you played the PS3 or 360 version of BL1 and wondered why one weapon (showing four lines of almost-similar bonuses) was somehow worth considerably more than another similar to it. Chances are there was a fifth bonus, or even a sixth bonus, on the item and there was no way to tell what they were.
I'm really glad that'll be fixed.