Are they SPD or SPD-SL? If SPD, go for it. If SPD-SL, think twice. The SPD-SL is the road version at it take a bit more effort to get out of quickly.
What's on my road bike is SPD-SL, but if SPD is the way to go for a MTB, then I'll certainly go that route. The guy I bought the bike from was going to toss in some SPD pedals for free, but I passed because I didn't see myself getting into clips anytime soon. *Facepalm