Well, they have removed veteran levels so no more grinding from vr1 to vr16, you are scaled up to max level in all zones so it's always a challenge (the zones are all at max), they brought in dueling, player housing, more group content in Craglorn, some really nasty hard trials, loads of new armour sets and costumes etc, crown crates (beware of these).
PVP is a bit broken at the moment though due to issues with unkillable tanks, proc sets that are over powered, heavy armour bonuses which are totally unbalanced etc etc etc.
I think most people are waiting for Morrowind to be honest, but there are also regular festivals such as the current Jesters festival, plus 4 man group battlefields are on the way.
I'm sure there have been more changes though.