Smoker might be no match for Doflamingo but I think he is one impressive guy!
Instead of answering the Shichibukai's question, he refused to betray Law and Luffy, even though they are pirates! In the process, he was badly tortured and now, his face is a wreck
We've always known he's one heck of a principled guy, but I say that's pretty cool.
While it's hard to calculate power levels, I've noticed one thing. All his opponents, even those who have beaten him, refuse to take him lightly and become very wary when he's around. While Doflamingo seems to be on a whole other level, even he seemed to know Smoker quite well.
It's interesting how Oda makes us respect a guy who, as others have mentioned, has not won a single major battle yet.