Yes, you’re right that with can be very useful — but to my mind, the danger of not knowing exactly what you’re changing outweighs the potential benefit. Personally, I would use the MooTools method of setting lots of properties…

var oMyElement = new Element('div', {
id: 'Fred',
styles: {
width: '100px',
height: '100px',
display: 'inline'
}
});

…which means that I can get away without using with. 🙂