One of the biggest things to remember about ribbon mics is that it has a ribbon, rather than a diaphram, so handle with care. Also, the ribbon will be much more sensitive to high sound pressures, and can be damaged by them. Generally, the ribbon mics are used in the studio, rather than live. With that said if placed right, there are plenty of applications for them. I picked up an MXL R40, just as an entry into ribbon mics (with my fingers, toes, and eyebrows crosses, hoping it wouldn't be a huge disappointment), and I have absolutely fallen in love with that mic. It's just perfect for my voice. I get an accurate reproduction of my voice, and I sound totally smooth through it (darn I say, "creamy?"). Finally, the best polar pattern for a live mic is cardioid, because it does a good job of preventing feedback. I can't say for all ribon mics, but the MXL R40 has a figure 8 pattern, so that it picks up some of the ambience of the room. That could be a disaster for a live vocal mic.