Another post on the top ten troll questions. This time, I'm tossing in the "bonus question".
(9). XP for gold, or XP for objectives (thieves disarming traps, etc...)?
XP for gold, definitely. XP for objectives? Not so much, although if an objective can be given a hit dice or monetary value, certainly.
I have suggested in the past that generic plans can be given XP ratings equal to 10 x the ability score relevant to carrying out the plan. However, I'm thinking now that I wouldn't want to apply that to every little task. "Oh, you picked a common house lock? Good for you. No, it's not worth any XP."
I've mentioned before that I don't see "level" as a knowledge or skill rating, but as a reputation and confidence rating. You earn experience by doing things that people talk about. Bringing back scads of treasure definitely counts. Picking one lock doesn't. Crossing the Horrible Desert? Well, yeah, that seems more reasonable; worth at least 10 x Con. Maybe also 10 x Int, if word gets out you did it because of your phenomenal knowledge about deserts. Disabling a well-known trap or opening a legendary lock should be worth experience, too. People talked about Alexander the Great undoing the Gordian Knot, so it must have been worth some experience points.
Bonus Question: Unified XP level tables or individual XP level tables for each class?
Individual XP tables, although I would only need four tables. Maybe only three; I've been considering merging the thief and cleric tables. Any other class is really just a variant of Fighter, Magic-User, or Thief, or a hybrid of two of those, so just use the appropriate table, or the one with the slowest advancement, for hybrids.