YMMV on protocols, just depends on what you're looking for. Most reasonable protocols you'd want are supportable. The only time I've been left scratching my head was trying to get the VM running on a SOCKS proxy, which I think probably speaks more to my lack of familiarity with doing so (though in the source of this I found that the native SOCKS libraries were removed some time ago.

We're using it at a client as a kind of nexus of all our legacy systems, in fact.