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)
you dont like lisp syntax? you want to do prototype based OO? they aren't identical. they may share some features but not all features. its sort of like asking back in the 90s- why would i use python instead of perl.
I'm curious to see the syntax (he says it will be homoiconic) and how that translates into the mechanism for manipulating the AST. This is the raison d'être for lisp's syntax.
Congratulations.... Since it's still "pre-announce" phase, I'll point out the collision with "Ceph" (http://ceph.newdream.net/), which may or may not be of concern to you and the team.