I use an old Intuos 2 at home and the pen is falling apart. I hate it. I'm counting the number of times that the button falls off and the sleeve falls down before I get fed up enough to spend money on either A) a new pen or B) a new tablet altogether. I hate to spend $70 on a stupid pen, but I'm having an equally hard time justifying the much larger expense of the tablet.
I do like the Intuos 4 though. I spent about 10 minutes scratching out this color sketch on a coworker's new intuos 4, and then spent another 20 minutes polishing it up on my rickety tablet at home. The quality difference between the two was pretty big, but I have to weigh that factor against how cheap I am. So at least for now, cheapness wins.