I loved it but was disappointed with how limiting the skill system is, something I hope is different in II. You have all these skills and, by the end of the game, enough points to maybe master one of them at the expense of everything else. I know part of the reason I enjoyed it so much is simply due to how rarely we get first-person dungeon crawlers, so I'm incredibly biased and willing to overlook its flaws. Legend of Grimrock II will also have outdoor areas and more varied environments, a la Might and Magic X, so I'm hyped.
This skill system was revamped as described here
It's a more standard one point per level immediate skill buy versus the allotting points down a skill line like the first one. I kinda liked the way the first one is so I'm less enthused for this one, but I understand why and don't hate it. Change is good.