Anyone here played/completed this? Any important info I should know before starting this, specifically any gotchas that could get me stuck halfway through the game?
I think you can pretty much go blind. There are not that many things to know beforehand, the game is not too difficut (combatwise) so any party is viable.
Some "tips" off the top of my head :
Useless skills : Fast talking (lets you skip combat via bribing the enemies with a successful check), merchant (there are only three merchant in the entire game and apart from the first they don't sell anything useful), pickpocket (same as merchant), acrobatics (only used in the rare "falling off a cliff" instances).
Things to know : automap is pretty unreadable and useless (particularly on maps with different terrain heights).
Ranged weapons are mostly used in close range (you hardly get a volley of shots or two before enemies close in) where they are quite viable but less so than melee weapons. So forget about making a ranged fighting party à la M&M. Too bad considering the steampunk aspect of the game and the firearms and steam weapons.
Some NPCs join your team for a definite amount of times only and nothing lets you know which ones and when they will leave. For info, the first one leaves at dungeon level 4 for instance. Most will stay for the entire game though.
Difficulty slider is a bitch. I could never manage to get it right. In the blink of a pixel it goes from "too easy" to "too hard", mostly for initiative reasons.
Some skills like "See secrets" or "Lockpicking" are used by the selected party member, so try to make a "leader" party member (see secrets, lockpick) and always have him selected when moving around. That way you'll see what secrets there are and open locked doors without having to constantly switch between party members.
INVEST AT LEAST SOME POINTS IN "CAST SPELLS" FOR EVERYONE AND PICK HEALING. Also, try to get "Aid" spell ASAP for at least one of your party members. Even at its lowest casting cost it will remove adverse conditions (poison, acid, disease) for the whole party.
EDIT : Feel free to ask any questions as you go, I'm not the Lilura of Thunderscape, but I guess I'm authoritative enough.