I like it also.
But I see an use case that this syntax doesn't really support:
Most infobox templates only show a row when there is a value to output, with a syntax like:
{{#if: {{{foo|}}} |
<tr><th>Bar:</th><td>{{{foo}}}</td></tr>
}}
but this inclusion syntax doesn't provide an easy way to know if a property exist. So, I believe that a "property-exist" parser function is needed to support this use case if we don't want to see things like:
{{#if: {{{foo| {{#property:foo}} }}} |
<tr><th>Bar:</th><td>{{{foo| {{#property:foo}} }}}</td></tr>
}}

I have also a question: what is the string identifier like "population" that identify the property in {{#property:population}}? the label in English? the label in the wiki language? an other string? Or is it only in order to help the reading of the draft and this string will be replaced by the numerical id of the property in the implementation?

+1 for a think like {{#itemlabel|lang=en}}. It will be very useful to output name of a creator in commons in various languages. A {{#itemlink|site=enwiki}} may be also useful to output links to Wikipedia in Commons and Wikisource (and links to Commons and Wikisource in Wikipedia).

Thomas

> From: g.m.hagedorn@gmail.com