it would sound like crap.
the figure of 8 pattern has a front and back, with the back lobe being out of phase. It definately sounds different than the front, but probably not in our application. Back when I was researching the Royer SF-12 stereo mic (ribbon blumlein stereo), I was sent a demo disc w/all sorts of studio takes w/their various figure of 8 mics. Lots of the tracks utilized this technique on guitar and vocals.
They (the engineers) were constantly tweaking the direction of the capsule to get a little different take on whatever they were micing. Sometimes it sounds best backwards.
but...for stereo recording, just set them up EXACTLY as if you were running XY. right mic is left channel, left mic is right channel. Instead of cardioid, you use fo8 and there you go.
The rear lobes of the blumlein pair are out of phase (as one lobe is left/forward where the other is rear right, and so forth), and it helps to provide that killer spatial sence that blumlein produces.
It can work at a distance as well. I pulled some pretty nice blumlein stuff w/the Soundfield from outdoor tapers sections way up in the lawn at shows last summer.
it shines FOB though. See Wes's 11-1 MSG panic recording for refference. sweeeetttt!
On stage? Forget about any other type of config (except M-S). it just so damn real, its scary.
Blumlein images like a bastard, provides killer soundstage depth and basicly will reproduce EXACTLY what you hear....so dont use it if you hear lots of room...because that is how your recording will come out. It is not one of those "unforgiving" stereo configs like NOS DIN XY..etc.