"Recently popular/hot content" list vs Varnish - Radioactivity?

I have been tasked with building a block of recently popular content for a site which will get a decent enough level of traffic.

The standard approach to this is to use the Radioactivity module, but I've been told to investigate other approaches; apparently previous experiments with Radioactivity on an earlier version of the dev site resulted in heavy database thrashing. I'm not entirely sure this was actually the case, since I didn't see it myself, and think I can talk my superiors into giving Radioactivity another try. However, there's another problem; we'll be using Varnish caching, so we'll need to work around that somehow. The idea of including a bit of JS that does an AJAX callback to the Drupal site to increment the hit counter (and just pretending that anyone browsing the site with JS disabled never existed) has been floated. I'm looking at the Radioactivity module code and thinking that maybe it supports something like that already (namely, the emit.php file), but I can't find any documentation on it anywhere… I note that this site states on its about page that it's using Radioactivity, and its HTTP headers imply it's using Varnish too… Does anyone know how it's wired together on this site?

Using Google Analytics Counter has also been floated, which makes sense since the site will already be using GA to count hits and such, so why install something else that does the same? But the code for this module is horrible; it depends on another module, Google Analytics Reports, which I could never get to work successfully; and this approach doesn't do the "half-life" thing that Radioactive does, so I'd have to hack that together somehow.

So are there other approaches I'm missing to do a "hot content" list on a high-traffic site?