I had my first generation iphone exchanged for a refurb, and the same with my 3g. I've never had an issue the refurbs. I would actually think that you have a greater chance having something go wrong with a brand new item than with a refurb. Can't speak for what the ipad refurbs will be like, but based on the iphone refurbs, you shouldn't be able to tell them apart from a brand new one. I don't think apple will release refurbs for several months at least. The ipads are selling like crazy, and the 3g version hasn't even come out yet. They are going to milk the profits from the full price versions most likely until demand levels or dies down, at which time we might see a slight price drop and/or the release of refurbs.
If you followed apple's earnings release this week, the ipad actually hurts their profit margin due to the ipad being a new product with the price of components high initially. (they are making a profit on the ipads, but less of a profit margin than on the ipods/iphones/macs, so it brings down the profit margin ratio) I feel that the refurbs, having been produced, and then repaired/restored again, are marginally profitable, if at all. Sorry for the tangent, I just don't think we'll see refurbs anytime soon.