It includes the ranger from SR, the paladin, thief, druid, assassin - character classes from the supplements. Still no illusionist, though, which was disappointing, but the SR illusionist just couldn't legally be duplicated. The game still runs on the 0e rules, not 1e. It includes two optional alternative order of combat systems in addition to the standard one from the WhiteBox era: the one from the Holmes Blue Book and one that's based on the EW system. Those are the main differences, although there are little things like adding strength modifiers to the amount of weight that can be carried, ala Supplement 1, etc. Virtually all of the additions are in the player section, not the referee section. It's compatible with the Core Rules, and the Core Rules will stay in place as the archetypal "three class" system....One especially nice thing is that our Druid class description is written by Dennis Sustare (the original author who invented the druid character class - think, "Chariot of").
Here's the basic scoop, though I may have forgotten something:
Mass combat (already there)
Order of combat - splits movement and attacks, but very close to Core Rules
Holmes Basic order of combat as an option
Eldritch Wizardry order of battle method (revised) as an option (rotating initiative based on what characters are wearing and doing)
Core Rules order of combat as option
More descriptions of things like wolfsbane
Wilderness adventuring, including getting lost, and monster encounter tables
Dungeon encounter charts now have specific monsters instead of just a CL listing
Dungeon encounter charts can also be used to generate mixes of different monsters (the orcs have a pet gelatinous cube! Run!)
No more wild boards in the monster listing
Building strongholds - prices for walls and keeps and such
Original saving throw numbers are listed as a chart in a side-box in case people want to use those.
Can't remember what else.