jimi_hendrix: I like exploring, dungeon crawling, leveling up, and finding nice loot. In an open world game, the story, voice acting, and graphics are secondary for me.
There is a lot of exploring, but most of the time you are outside. There are definitely dungeons, but they're usually pretty small. However, there are tons of enemies to fight in the outside world, and there's TONS of loot, plus the game's stacking system that lets you combine weapons or armor together to improve the stats. I found loot collecting to be the most enjoyable part of the game. It's similar to Diablo in terms of the amount of loot.
Early on there is little variety in the environment (woods and mountains) but once you cross the river you'll visit a lot of diverse locales, like swamps, bamboo forests, beaches, wastelands, spooky graveyards and a desert.
I think the horrendous reviews were mostly due to bugs. Those are pretty much fixed now. The game isn't incredible but I found it to be fun.
I recommend trying the hardest difficulty setting as otherwise things are a bit too easy. But the early game can be tough on the highest setting.
Also if you decide to get the game be sure to check out some threads here on GOG about some simple fixes you might need. Many players have issues with PhysX and need to do a quick workaround when installing the game. Also, most players find the lip-synching is off; this is not GOG's fault but was actually introduced in the final official patch for the game. A simple file swap is all that's required to fix it, and you can find the replacement file here in the GOG forums.