I really don't like the idea of a passive DI for guitar. Typical input impedance is usually too low, and the step down through the transformer takes an already slightly low signal and attenuates it so that you need to add a bunch of gain on the other end. That can only add noise.
The Countryman is active, though, which is better. In active mode the in-Z is plenty high for anything you'd realistically plug into it. It does seem to attenuate the input by 10db. Not as bad as a passive unit, but still likely needs to be compensated. Consider that the Instrument/DI input on most interfaces add about 10db, so if you want to get from the Countryman back to that for whatever reason, you need 20db. Again, this will add noise, but not quite so bad as the passive. Keep in mind, too, that while a 5V p2p input ceiling is probably fine for all but the hottest of overwound humbuckers (I might start to worry about series combinations of hot humbuckers...), it will be possible to distort the thing with an active preamp like an EMG system, or acoustic-electric or active bass. You'd also have to be careful with things like keyboards and line level sources. None of those things would really need a DI to begin with, of course, but some folks...
The balanced output is nice if you need to run a long cable to the recorder - down the snake from a stage or in a big multi-room studio. In most living room/bedroom/basement scenarios, though, it's not completely necessary.
But what are you doing with this DI signal anyway? Are you looking to actually physically reamp at some point? In that case you generally want the signal that goes to the amp to be the same level as what came out of the guitar. So you use a DI, which reduces the level, then you add gain at the mic pre to get it back to a decent recording level, then by time you get back to reamping you don't really know what the original level was, but you probably have to attenuate anyway. All of that could be avoided if you just run unity from guitar to interface, through DAW, to amp. The best way to accomplish that is to just buffer the guitar (any big name pedal, powered but off) into a line input on the interface.
