I spent labor day weekend in Boston, had most meals out, and didn't have any trouble. The hotel meals I just signed to the room. They included a mandatory 18% tip for the place, and I've been there before and didn't mind it. Service was great. The other places had the card readers that you'd tap and the end and could select a tip. I have a debit card that I only use for traveling and little things that I use for that. All added up fine. Little things I just used cash.
There's only one bar where I've ever used a credit card to run a tab, and that was because I knew the bartender from a previous bar and followed them over to the new one. Otherwise I'd never do it. If I'm having a drink before dinner I'll either pay cash or ask them if they can add it to the dinner bill.
Good to know to look out for extra drinks, though. I'll keep an eye out.
One positive note on the mandatory tip - there's a seafood boil place here that has some minimum tip, and the first time we went there the waitress made a point to tell us that the tip was built in, so we wouldn't accidentally over tip.
Oh, and as far as other staff taking tips, I've heard of it happening around here, too, from time to time. The sit down fast food places, typically. So my normal thing at a place where you pay at a cashier but tip at the table, I make sure the waiter/waitress sees me leave the tip so they get it before the person at the next table or the hostess does. Places like that I tip cash always, because cynical me doesn't trust that the front desk actually gives all the tips on the CC to the staff.