By just priming, did you do it today/yesterday? I'd expect two things then, that the beer with taste green at the worst, sweet at the best, and that if you force carb, if the keg isn't finished, they'll still be producing co2 that you'd have to vent.
You know those posts where people know their beer tasted good, then they bottled and tested it a week after, either knowing that it's not ready but curious, or they don't know better and they complain about it tasting wierd and horrible? That's what will likely happen, but carbonated if you force carb.
Got any other spare beer?