I used Pixie for a little bit. I didn't get the picture that the dynamic nature was the issue with it, more a lack of libraries bound and a lack of time to optimize and steward the system.
Pixie is great if you also know which C libraries you want to use, but it's not super friendly to people who don't know which C libraries are best for the job or people who just want to consume a library.
I've been meaning to take some time to try out Ferret and compare it against Pixie for wrapping C libraries for a systems language.
Yeah, he mentioned that it was an optimization problem, I never got a good chance to look at it, but even something that was feature rich, and tied nicely with native libraries could have been a game changer for some of the markets that clojure sucks in right now.
Clojure's horrible startup time really gives a leg up on a solution that ties closer to commandline scripting tools