Anyone have experience with Wushu?
The main downside is that Wushu is a narrative system.
That means it only works for certain types of games - the one that focus on story rather than say tactical challenges, or kicking behinds, or acquiring loot)
On the other hand some story heavy games are fairly hard to do with WuShu, for example a murder mystery is rather hard to run when players are allowed to find clues of their own creation. (With some practice and players willing to cooperate it still can be done though)
It only works for certain kinds of players If you have someone who loves reading class and powers books, optimizing her characters, paying close attention to mechanics to gain an edge - WuShu will be at best an exercise in boredom
It relies on quality of storytelling your players can provide (as Redfoxmagi already mentioned). If players aren't willing or able to create good stories - you won't have a good game.
Narrative progress resolution rather than success/failure one will be unfamiliar AND uncomfortable to many players.
Narrative Truth could make the game harder to steer, the game has checks and balances to help GM, but the game could really veer off when you MUST accept events as players describe them. That's not always a problem, in fact in an established group where you know you players well - you'll be fine. ;)
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The main upside of WuShu is that it's narrative system. ;) :P
If what you are looking for is something to give structure and direction to a game which is essentially collaborative fiction project between friends... if what players want is to take part in a story - WuShu is great
It works well for PbP, the focus on story makes, say, a round of Descriptions every few days feel like a well progressing game, where crunchy systems might require nearly real time exchange of dice rolls and results just to keep a single round of combat from stalling the game.
Another advantage, it's easier to be "playing GM". Narrative Truth gives players more power, which often means you don't have to stay outside the game as a arbiter and supplier of content. You can set the scene and then join your players with little harm to the game (but you do have to control the urge to metagame)