I've only used my Sennheiser e604 on tom drums in the studio, but I could certainly see them being used live because of the convenient clip. Since it is a dynamic mic they would probably work on guitar amps and snare drums as well.

OVERALL OPINION

I've had my Sennheiser e604 for about a year now. My favorite part about it is that it has a clip that you can easily mount on to a drum. Although if I had the money I would prefer to have another Sennesier 421, this really does the trick on tom drums, making for a very full sound at a pretty reasonable price. I would use this on a tom drum over a Shure SM57 just because it is easier to set up, but if I had extra 421s I would definitely use those, however, until I can afford to upgrade, the e604 definitely does the job I need it to.