afaik the worst of the memory leaks were fixed with the 2.0 release, and they also upgraded QtWebKit to 5.3 which fixed some pretty egregiously outdated constraints (like not having access to Function.prototype.bind) present in the previous version. Sadly this tool utilizes phantomjs 1.9 which means the memory leaks are still present and major WebKit features are still missing.
One great use for headless is to separate non-UI framework/platform tests from UI tests - at my previous gig we wrote all the tests for the runtime platform against phantomjs to avoid the unneeded overhead of a full browser for things like data validation or mocking service calls, but used selenium to do the visual/interaction tests for the application UI itself. it's also a nice separation of concerns, though of course we hit all the same problems you mentioned as we were also pinned to 1.9.
One great use for headless is to separate non-UI framework/platform tests from UI tests - at my previous gig we wrote all the tests for the runtime platform against phantomjs to avoid the unneeded overhead of a full browser for things like data validation or mocking service calls, but used selenium to do the visual/interaction tests for the application UI itself. it's also a nice separation of concerns, though of course we hit all the same problems you mentioned as we were also pinned to 1.9.