Something you say to let your friend know that even though he is listing someone's positive qualities, you know he's only doing it to set up a jab at that person.
Friend: Ya know, Chet's a really nice guy and lots of fun, and he's always willing to buy the beer and share it with everyone...
You: I smell a 'but'
Friend: ... but he drinks too damn much and I get tired of having to take care of his alcoholic ass.
What a lovely day for a 4421744! SCK was here