I've been to Maxwell's several times with my family. Every time the food has been really good. Wait time can be a long time, but we have come to expect it since it's so small.
Recently we went for dinner. Being a big beer geek, before I order a beer I've never had, I like a small taste (less than an ounce) to make sure I like it before dropping $5 on a crappy beer. I asked for one and they promptly stated 'we don't give samples'. I could have a flight instead. Well I only wanted one beer, not 4 small ones so I just said I would drink water. The owner comes back with a small shot glass 'we don't normally do this, just so you know.' Guess it was my 'threat' of drinking water that changed their minds.
My wife ordered a pita with ranch instead of the sauce that comes with it. They charged us 50 cents for the substitution.
I ordered a burger off the chalkboard (didn't even need to check the menu) for $10 and asked if they had onion rings. Waitress said they sure did. Got the check and the burger was $11.75. Asked what the added charge was and she said for substituting the onion rings for the fries and said that the upcharge is listed on the bottom of the menu. Well I ordered off the chalkboard! Would have been nice to be alerted 'we have onion rings, but there is a slight upcharge'.
I just don't like to be nickeled and dimed for stuff. Be upfront. Tell me there's an extra charge. And any good tavern/bar/brewery will let you taste a beer before ordering it. Heck dock me a shot when you pour my beer if you have to!