I have used them for training so yeah, I'd race on them. I'm not a heavyweight and ride "light" but Shimano builds great and solid wheelsets. Have a set of the 7801s that I've had on some rugged stuff. No issues with those either. GO!
Good enough for Jonathan Page to win nat's on ... probably good enough for me! Shimano builds some of the best wheels I have ever ridden ... they are bullet proof.