It's the novelty effect at play here. I would imagine they would actually be at a loss every time they accept bitcoin payment. The restaurant can save 3%-5% from card fees, but they could loose out on exchange rate and conversion fees. Bitcoin a great marketing tool. I would dine in one of these restaurants if I have a chance and have fun spending bitcoin.

I hope they accept zero confirmation payments? I do not want to wait around for confirmations. We all know there is no telling when the next block will be mined.