Your map convinced me to dust off my 5 year old forum account, so you can feel proud about that. Stellar map, loved almost every minute of it, and I'll probably boot up the 2nd rendition once I finish here.
A few thoughts:
Boss fights felt hard. Really hard. For all but two I found myself unable to even attempt the battle and had to put myself into creative to finish the fight and sometimes even then the boss absorbed far too many sword hits. Meat shield damage sponging bosses are just annoying, especially when you're being tailed by dozens of respawning minions. An example is the fight near the end of the battlefield area, with the skeleton riding the baby zombie. The fight itself wouldn't be annoying had there not been 40 zombies standing in front of him making it impossible to get to him. Perhaps consider objective based boss fights. An example is the King Dodongo in Ocarina of Time. Avoid his attacks, and make him swallow 3 bomb fruits to win the fight. Doing this instead of forcing me to just swing and swing at the boss could make it more rewarding to figure out his weakness.
Areas were extremely well designed. Some favorites include the volcano area as well as the Ethos and Sethbling lab. Your area designing skills are impeccable and I'm sure that will only get better in TR2. I won't suggest anything since that makes me sound like a fanboy, and I trust you to create some great landscapes for the second version.
Loot was good. Some junk mixed in with good, useful loot. Loot served its purpose well and I don't foresee any huge changes to it being necessary in the new version.
One thing which did puzzle me a bit were the negative buffs applied to my character in some of the last dungeons. After receiving the permanent buffs following Road of Triumph (permanent buffs, on a side note, are amazing, and make it feel like a real RPG experience. Definitely continue using those.) I entered the crypt dungeon and found myself immediately having my buffs canceled out by permanent negative buffs throughout the dungeon. I'm sure there was a reason for this which is not clear to me, but I wasn't a huge fan of the idea of just having my strengths canceled out across the board.
Otherwise, everything else about the map was fantastic. Left me feeling really good at the end, and I think this map might be one of the things I look back on nostalgically about Minecraft. Keep it up, can't wait to play the next one.