As much as I respect Ola Bini's projects, I have to ask: what reason would one have to use Seph instead of Clojure? They seem to have the same design goals (homoiconicity, immutability)
Congratulations.... Since it's still "pre-announce" phase, I'll point out the collision with "Ceph" (<a href="http://ceph.newdream.net/" rel="nofollow">http://ceph.newdream.net/</a>), which may or may not be of concern to you and the team.