Lately I've heard a lot of talking about 'bennies' in RPGs. Mostly this is in the context of how wonderful bennies are and how they enable the players, and also how they can be used to drive 'roleplay'. I don't hate this mechanic but I don't like it either and I certainly don't think it's all that, like people are making it out to be. I generally dislike luck points, bennies, fate points, or to a lesser degree, point spending in Gumshoe because I think that they often mix poorly with dice roll mechanics and they cause people to horde the points to use either for re-rolls or to buy victory. Buying a victory or a reroll is not bad in itself, however usually the economies used to pay for these points are a bit borked. Generally you get bennies for doing something interesting or funny and then you use them to take the edge off those situations where a poor dice roll would be very... well interesting or funny. I'm not saying that I'm right about this, it's just my perception of these mechanics that they let the player earn and buy security. I can see why this is popular, everyone wants to control their destiny and having a good idea get blocked by poor rolls is a bit of a bummer. I think that in a dice based game the best way to mitigate risk is to avoid rolling the dice in the first place.
As for XP, people seem to think that you should award XP for fighting (fine), treasure (ok if done right), and for roleplaying (good in theory). The idea here is that the game play will be shaped by the reward mechanic and unless you want a game all about fighting and money you should reward roleplay. However it's hard to reward roleplay because it does seem to be very subjective. I would much rather award XP for goals completed than for staying in character or clever roleplay. Also if you do award XP for goals be sure to indicate the kind of goals and the payoffs upfront in your campaign or it risks becoming capricious.
All the commentary I have heard discussing this subject seem to reinforce that rewarding roleplay works if you have a good GM but otherwise not so much. I'd say it isn't the caliber of the GM as much as it is having a GM that wants to track all your RP and special snowflake moments. Lots of good GMs are not interested in tracking all that stuff. I've always been intrigued by the notion of awarding Experience for Damage as outlined by Alexis S. in Experience Solved. This system awards XP every time the PC takes or deals damage and it is a great idea. I certainly like the objective way that the XP get handed out in that kind of system and the only reason I haven't tried this out myself is that I don't like the idea of tracking things so much. Lots of work keeping track of things.
This dovetails in with the idea using a mechanic to reinforce good game play by rewarding characters taking actual chances instead of pretending to take chances. In this case however it isn't handing out bennies or fate points for players acting, but rewarding player action - having the players rolling dice instead of playing it safe and avoiding the dice roll.