For me, it's a question of how much time do I want to waste on an auction where the Reserve may be much higher than I'm willing to pay. To win auctions at a good price, you have to remember that your bid may stimulate others to bid as well (even below Reserve) and you have to continually Watch these auctions, rebidding, and maybe Sniping them if you hope to win.

Since only the Seller benefits, I don't consider bidding on Reserved lots at all unless the Reserve price is disclosed (as with Club auctions).