So it's been years now since the Simple Machines dev team started working on SMF 2.1. A lot of work has been put into it, including new features that I'm sure some of us will appreciate very much. They also tweaked the design of the forum as well as the interaction to make it more modern.
I decided to check out for myself how good it was and went a step further and installed the latest version of SMF from their codebase. (It says SMF 2.1 Beta 3 but that hasn't been publicly released yet.) This is also a good way to check it out for yourself and see how you like it.
More information on the features of SMF 2.1 can be found here:
http://wiki.simplemachines.org/smf/SMF2.1:FeaturesAnd of course, here is the link to the forum so you can test it out yourself!
http://beta.innectis.net/index.php