I gave up on varnish years ago. I got fed up with it yellowing, being too glossy, and eventually splitting and even lifting like old dried gloss paint (I'm talking about years and years later). I found oils to be much easier to apply (and repair), and swapped over to them almost exclusively.
The pendulum may be swinging, though, as I am now getting a little fed up with the dull finish of oil, which gets easily stained, especially by liquids. I know Paul (Pinch) uses varnishes a lot, so I am after a bit of a discussion on their merits, particularly now that so many of them are water-based, and are available in semi-gloss (and even matt, I think).
So, what should I be buying, how should I be applying them, and what is the general benefit of varnish over oil and/or wax?