Yeah hardware switches work just fine... you dont need to share the screen, you just dont have to connect it, but if you want to save up by sharing the mouse and keeboard you might as well share the comp screen... if you have another one what you can do is then connect it to your main comp for a bit more desktop space =p
i think you can consider 2 types of switchs... the ones who use USB and the ones who have PS/2... some switchs also can share 2 way speakers...
by the way if your thinking in buying a switch may i recomend that you buy one that has all cables going to the back... some switchs have ports in the front and are a pain to set up because of all the cables running around the desk