Why?

I like the approach to managing a site taken by Jekyll. A lot.

I don't like Ruby, and I don't like strict logic-less templates. Jekyll is Ruby with Liquid as the templating engine.

Heckle is JavaScript with Mold (programmable template extravaganza) as the templating engine.

Don't use Heckle at this point if you want something stable and finished. It's a work in progress, and may be radically changed or pitilessly abandoned at any time.