i've use it when the situation calls for it, not so much as a room mic but more of an additional mic to enhance certain frequencies, my goal when recording guitars is to use little to no eq adjustments, i usually mix 2-3 mics, i tend to use 2 dynamics+1 condenser. i'll set them up with the following starting point, have the 1-2 dynamics(sm57 and/or md421) close mic'ed, then listen starting at about 12-16 inches from speaker with the condenser, it does act like a room mic by picking up the sound of the room and less of the direct speaker.
the technique can bring a world of ease depending on what your application and tone your looking for, i like heavy full bodied guitar tones(eg mids) with a little upper frequency clarity, so a majority of the tone is coming from the close miced dynamics, but i use the pushed back condenser to pickup a bit more clarity, not too much just only like a 10-12% mix with dynamics.
but you have a good selection of condensers to use for this application, anything with at least a 150db spl rating.
but my reasoning behind using this technique is that i hate eq'ing mics, if i don't have to i won't, so thats why i mix multiple mics to give me the tone i want and with little to no eq at all, when recording i mix the muiltiple mics into a single bus, so what i achieve is the tone i want, no eq in most cases, so i just record the track and off i go.
but major factors in using this technique is dependent what type of tone you want to achieve, a lot of the tones can be done much simpler, but if you like messing around with the eq all day thats your choice, this technique also requires a lot to consider, everything from speaker choice to room choice to mic choice and mic configuration.
