alpha11 introduced specs for common macros, so bad ns/let/defn forms will now fail to compile. We use a fork of http.async.client, which has a bad defn. This is fixed in the canonical project but not yet released. We probably need to pull that fix into our fork and rerelease, and evaluate if we even need that fork once the canonical project is released.
We may have other alpha11 issues once the build gets past web.