At the moment, we're mostly developing and testing against Firefox desktop release (currently 13) and nightly (currently 16), along with Chrome desktop release (currently 19). Over time, as we get more automation in place, we'd like to support most or all modern browsers, desktop and mobile.
How fast do Gladius-based games run?
Surprisingly reasonably, given that we have not yet spent much time at all profiling or optimizing. We'd like to see automated performance tests in place before too long. If you're interested in helping with that, come talk to us in IRC or on the mailing list.
Does Gladius run in node.js?
Gladius is a client-side engine, which means it runs entirely in the browser. Node is used for linting, building and minifying the engine. Parts of the engine will also run in node, and we may expand support to node in the future for server-side applications.