I've been building Shopify themes for the last couple of years. Part of the reason that I've stuck with it so long is that Liquid is really easy to learn. I'm of the opinion that anyone capable of understanding a for loop and if statement can learn the basics of Liquid within a day.

I know there are a few other apps that use Liquid, including one of your competitors. See here for a list: http://github.com/tobi/liquid/wiki

From an end-user perspective, I'd highly recommend Liquid. I don't see how you can escape having a template language of some sort, and Liquid seems more thought-out than most.