After the first headset try, I simpli can't live without. This is because I often need to look where my fingers are, and this is a problem with a classic mic. Moreover, I have three keyboards stacked, and it is not easy playing the lower one and singing.
I'm currently using a Sennheiser, but I'm waiting for an AKG to give it a try.
The standard mic is still present, connected to a KORG iH Vocal Harmonizer, which is midi - drived by a KORG X3. So, when I need more than one voice, I sing in both mics (the headset is at the right side of my mouth) and play the X3 (wich is at the top of the stack!)
So things works as long as I keep this setup.
;-)