Track lighting can be used in a kitchen and I have seen it done. The light spread can be diffused somewhat buy getting wide angle lights and diffusers. Track lights can also be used in a bathroom, but I would not recommend it. They are not rated for wet locations and bathrooms can get pretty steamy.
You can put as many lights as will fit on the track as long as you do not exceed the rating of the track or circuit.
I only recommend track as a last resort because they are not a good selling feature. If your concern is a vaulted ceiling, look into low voltage lighting.
Also, if you do put track in your bathroom, The track must be at a minumum 3 feet away from tub edge and a minimum of 8' above tub rim.