I suppose the ideal is to actually track in such a way that you can put the faders at unity and have most of the mix done. At a certain point, though, one wonders why we've even got the damn faders to begin with!
I personally find that there are plenty of places in the chain to adjust the overall level before it hits the fader. Any plugin with an input and/or output gain or level control can usually be pressed in the task, usually while it also does whatever else it does. I'm sure that thing has some nice features, but to my mind, multiplication should be free. Unless you're really looking for something other than straight gain - non-linearity or filtering - I can't think of a good reason to actually spend money.