I own a Wacom Graphire2 and it has THREE buttons (a left and right button PLUS a clickable scroller wheel!) all for only $99. And even without Wacom's drivers it all works fine. Wacom has X beta drivers out (its feature set is great but I've noticed a few bugs in the beta so I removed it for now -- but it DOES work).
Best $99 I spent in a while... also comes with TOUCH-SENSATIVE pen (with eraser!).
