"Learn from your mistakes." I find it odd that a character's success and growth should only hinge on combat success. As such, I don't mind rewarding XP for failed combat ("Well, let's not do THAT again!"), finding traps - whether by clever investigation and disarming or by a good, old-fashioned 'Oops!" and role play.
As a DM, I'm a fan of milestone leveling. There's much less accounting for me and I tend to think of levels as 'chapters.' When a chapter is done, the characters should level or receive some other reward. Then I design enough combat encounters to get the characters 'in the neighborhood' if I were doing XP and I assume that the rest of the XP comes from role-play, finding traps, exploring the area, etc.
As a player, I must admit that I like when the DM at the end of the session says "You all get x Experience for tonight's session."