The best alternative I've seen is Adobe Brackets (http://brackets.io/). This is Adobe's IDE that gets regular builds and is essentially the nightly build of their new Edge Code IDE (https://creative.adobe.com/products/code). The newest plugins come out on Brackets first, then make their way to Edge.
The best thing about Brackets is its built in HTML,JS and CSS so it opens up a huge development community for plugins.
Interesting that WebStorm is only $49.99 for a single license and $29.99 to renew versus ST2 is $70 for a single license and the upgrade cost I believe is $70 as well?