Don't get me wrong, I love SMF. I'm quite fond of this software having used forums powered by it 7-8 years ago. It's nice, and it's functional, but these days there are far better alternatives.
Two examples I'd recommend considering are IP.Board and XenForo. IP.Board is the most aesthetically pleasing forum software I've encountered ever, but it's loaded with bugs and problems. Whether or not that will be easier to deal with in their upcoming version 4.0 remains to be seen. Their purchase plans are all quite expensive too, which is a definite drawback.
I don't have as much experience with XenForo, but it is visually appealing and very functional. I like it better than SMF, but it's not as intuitive as IP.Board's design, in my opinion. That being said, the software seems to be less buggy and it is highly customizable.