There's a few new minor properties that drop on new artifacts, but otherwise it's the same. Suits tend to be a bit more buff with the introduction of the Imbuing skill (from the SA upgrade). Hit Mana Leech and Hit Life Leech are the big exceptions - their displayed value is now based on the actual property value modified by a factor for weapon speed (including SSI), and apply every time (leeches base amount for property times (1% to displayed value) each hit). SSI acts as additional Stamina for swing speed calculations (With each 30 stamina counting as a 1 tick reduction).
The Stygian Abyss dungeon is popular, with mini-spawns, two new Champ spawns (fel rule-set - you enter them through portals from the Tram-ruleset dungeons, or the Fel dungeon to dungeon teleporters), and new Peerless.
Peerless were introduced in the expansion after SE (ML) - essentially instanced bosses, with little or no helpers, but powerful attacks and tons of HP. They drop artifact-like items as well, of their own. Some people can solo them, but they are meant for team hunts. Both the ML & SA Peerless retain popularity due to unique drops (look up "Crimson Cincture" and "Tangle" on the main UO Stratics site, for examples).
You have access to everything up to and including ML right now. SA stuff, you will have to wait for until you pay for it. There's also a "High Seas" add-on, if fishing and pirate hunting interest you.
There's 3 race choices now - human, elf or Gargoyle. Elves have bonuses that make them the preferred race, primarily because the Devs keep nerfing humans, in misguided attempts at PvP balance that only serve to marginalize humans in PvM. There's way in-game to change back and forth between human and elf at no cost, but changing to gargoyle requires tokens that come from the SA expansion gifts.
Spellweaving and Mysticism are two new spellcaster skills, and you need to get with someone in game to best explain those where they can be demonstrated. Mysticism functions similar to Magery, and uses a bunch of older stuff (and a couple new items) for reagents.
Chivalry got recently altered, and steps were taken to make hybrid templates less powerful in PvP (again, to the detriment of the PvM users of the skills).
There's now "Greater Dragons" - 5-slot beasts that are a pancake to tame, and nowadays the go-to creature for most taming situations.
Housing is still pretty much the same (some changes to house placement after another drops, mostly), with a few more style options. We're hoping that the Account management system changes going on right now will cause a lot of the broken houses belonging to people who quit years ago to start decay. If you were here in January 2004, you might remember when that kind of "housecleaning" happened last time (aka the "great IDOC party of 2004", with dozens of houses dropping near-simultaneously on all shards).
