The few times I've been to an iPad place, I've always had a server come and take the actual order, bring plates and drinks, and check back a few times. The iPad thing was only for payment. Normally I see what the 'suggested' tip is (often 15-20%) and I adjust according to the service received. If it was of a reasonable standard, I'll leave the tip where it is. I've never had really poor service, but I've had exceptional service. So I bumped it up to 25%. And I was happy to pay it.