The driving philosophy of these engines is that your presentation layer should not contain any logic that goes beyond the rendering of data, and your templating should be an aid to outputting HTML, not merely a medium.

Take Django templates, for example: you output data using tags and filters, with support for defining commonly-used blocks of HTML to reduce redundancy. Take Haml, which uses CSS selector syntax to reduce the amount of HTML boileplate to a bare minimum.

The common factor of these engines is that your end up writing less code than plain HTML, and unlike this new engine for ASP, the mixing of code and presentation doesn't look completely horrendous.