Now for the point-counterpoint:
Stand mounted mics MAY transmit a small ammount of residual noise IF the kb stand is not solid, and IF you bang real hard on the keys, and IF your mic is set too loud.

Many, many players (including DNJ, Fran and myself, on this forum) have used this method for YEARS with no adverse effect. The trick is in the construction - you need a good solid, bounce free envirnment, and you need to have the proper settings on the mic levels. Singing over a kb with internal speakers requires that the mic technique be a "close" one. Kissing the mic, if you prefer. That allows the most signal to enter the mic with the LEST amount of outside noise allow with it. Headset mics reduce feedback problems, but there is not even ONE model that comes close to the quality and sound that a hand held mic can provide. If you are willing to sacrifice vocal quality and mic technique ..... a headset will provide you with less feedback and a small amount of ease of set up .... if you like being tied to the amp, and feeling like a hospital patient with a monitor in your temple. ( )
Needless to say .... the headset is NOT for me.