I'm no fan of early access games, but actually, this one is a definite exception to the rule. I got this in the Roguelike 2 Humble Bundle (so it was something like £4 for this and other rougelikes), but this was the game I was looking forward to. I'll quickly list some pros, cons, and then my experience.
• Really good combat system with a focus on timing (nice balance of annoying bats and poison worms, and non-annoying enemies).
• Levelling up and getting loot works well. You sometimes get a rare piece of kit, which makes you feel like god for a few floors.
• Very attractive game (although there could be a little room for improvement in some of the room details), chunky pixels are officially cool. The first, second and final themes work really well. The third theme is a little pedestrian - and so dark you just can't see anything in it.
• Music is great, very fitting but not in-your-face-y.
• Foremost: almost all of the game is just so dark. There needs to be a 'Scroll of Light', or an update making the Candle light up the world a little more. In the third 'theme' (I won't spoil it), it's so dark that you often can't see any monsters, especially as only a few pixels aren't hiding in the water.
• Jesus christ, the poison goes on for years.
• Very little point in not choosing to level up HP when you get the choice. I went from 8HP to 38HP (ish) in one run-through, and if you wear the armour you just find, you basically don't need to worry. If you don't, then the poison (above) will easily kill you.
• No way to block with your shield? And also, 2handed weapons don't seem to do any more damage, to make up for not having a shield? And - equipping books as a shield feels like it should do something, but no notes anywhere make it clear what (if anything) having a book equipped does.
• Regardless of the above things: I finished the game in my first run-through. If you can't be bothered (e.g. at the end of the fourth 'theme'), you can simply run past enemies and take negligible damage - less so than you would if you tried to fight it, especially seeing regen items are so rare.
• And least importantly: this game is evidently unfinished. I understand it's a roguelike, but it does need a bit more content. If you could fetch the orb, run back to base, then go on another mission (assuming the orb unlocks a 'new' dungeon), that would be cool. Or challenges, modifiers, things to unlock, weapons to start with, etc., that would be awesome. I just feel like I couldn't play through it again. Maybe levelling up should unlock cool spells, or something similar? I don't feel like I need to grind or farm in the dungeon to look for some awesome and rare loot that makes me godlike. It needs something rare like that, or something that unlocks. In my opinion, that's how Risk of Rain is just infinitely replayable.
TL/DR: I still would totally play it again, but it's relatively easy to finish in the first play-through. This game is already good, and I'm assuming it'll be great by the time it's out of Beta! :-)