My eventer-in-training, Smoke, is barefoot (as in not wearing shoes, I don't mean we have a special "barefoot farrier") & has been for his whole life. I see nothing wrong with competing at the lower levels without shoes, as long as a horse has GOOD feet. The questions asked of them on a BN course aren't exactly rocket science, and the courses aren't long. However, I don't really know the condition of your horse's feet, so what I think is okay for my horse may not be the best decision for yours.
I also agree with Kevinshorses - if a GOOD farrier is putting shoes on your horse, then no harm will be done. Incorrect shoeing is what causes problems.