I'd go so far as to say 'just use Handlebars', as at some point you will need an 'each' construct which underscore templates don't provide. They're okay for minimal templates that are akin to string interpolation, but as soon as you 'get serious' you end up writing things like <% _.each(things, function(thing){ %> which is just horrible.

Mustache-based templates (mustache, handlebars, hogan.js), though they are a bitch in their schooling you on being 'logicless' really are in my experience, very practical.

And please no-one downvote me by nitpicking that templates can never be truly logicless, I know that :)