I am a huge fan and follower of Kier and Mike's Xenforo. In case you do not know Kier and Mike were former vBulletin Lead Developers. Their own Forum solution, Xenforo's release dates have just been announced.
We have learnt that Xenforo Beta 1 will be available for purchase from first week of October. There's a 24 hour early adopter's discounted price of just $100!!!!
Xenforo is the most modern, lightweight and amazing forum platform in the market! You got to grab it within the first 24 hours.
From then on the price is $140. And what's more, support period starts from day of Stable release for full year and not from when you purchased! That's even more incentive to just get it at 100 bucks!
Full announcement is here