As above - I love Smart, but if I had a chance to make this deal, I couldn't say no.
Butler gives us that go-to scorer we've been desperately needing AND he's an outstanding defensive player too.
With Thomas, Butler and Crowder we would have (easily) one of the best backcourts in the NBA. I think that trio gives Curry, Thompson and Barnes a VERY hard time. With that core in place I think we could beat the Raptors and Cavs in a 7 game series...and I think we'd be a one quality defensive big man away from being able to seriously compete with the Warriors and Spurs.
Giving up Smart and the Brooklyn pick is a big risk, but Butler is worth the gamble.