Mo Facta
Farts of Nature
I have to admit, it's been a while with those and maybe they've made some upgrades -- But wow... Hated 'em. Just hated 'em.
I'm a C1000 apologist. I used to be a big hater of these mics until I tried them on things other than what you'd think they'd be aimed at. They're FANTASTIC on electric guitars, particularly clean and edgy blues guitar. They're a very good toms mic too.
And, for a bit of interesting info, Maynard's vocals on Tool's Undertow were recorded solely with a C1000. I shit you not. Check out the Sylvia Massy Q&A on Gearslutz.
But yes, they are not good for everything, particularly overheads, which is what they're mostly used for. If your cymbals even have a smidge too much copper in them they're going to sound like tin cans. My theory is that because they're a cheap mic they make it into the hands of a lot of novices so they get a lot of flak for bad sound when it could very well be the bad micing technique of the novice.
Piano? I think they'll do the job. The piano has beautiful overtones. If the source is smooth, the mic's response will have minimal effect and you'll probably get a pretty decent piano sound.
They're better than nothin.
Cheers