CVG: Should you be concerned that the introduction of this most 'traditional' of elements will somehow cripple Portal's hermetic intellectual appeal? That it will somehow become dumbed down to shoehorn in a feature for the masses? Of course not. This is Valve, you ninny.
In gameplay terms, your duo of co-op bots gives you four portals to work with rather than two - but you're going to need all of them. Although the puzzles are naturally more complicated in design - you've got two bodies to get from point A to B, rather than two - the helping hand helps even the score.