Since an embedded JavaScriptCore can be made to launch quickly, I've been pondering whether it is justified in converting Planck to be a portable (OS X, Linux, Windows) C-based wrapper around JavaScriptCore (so that it is more broadly useful). Right now Planck is not portable owing to the use of Cocoa/Foundation and Objective-C.
I think this partially boils down to wether the launch latency is faster than an equivalent based on Node.js (which is already portable and has a much richer ecosystem). That latency has to be significantly different, and I also think you'd need to be convinced that it is going to remain that way (perhaps V8 will be further optimized, but perhaps the outright launch speed of Node.js isn't a priority).