I've had a Happs top fire in my Virtuacade Mame cabinet (
www.virtuacade.com) now for several months, and overall I'm very happy with it.
True, the spring action is a bit light and springy, which may make precise fighter game moves a tad trickier, but with all 8 way games, it plays great! And like most people, I originally bought mine to play Tron properly, which it does allow.
One thing that pleasantly surprised me about the stick is that it plays 4-way games like mspacman incredibly well !!! Because the stick is lightly loaded, you rarely get those "sticky spots" when you lean diagonally. I can play the fast-hack version of mspacman without a hitch using the topfire, whereas my Happs Competitions occassionally stutter. It all has to do with the construction of the contacts within the joystick.
My ownly complaint with the Happ topfire is that it's a bit uncomfortable to hold the "tulip-style" stick between your fingers and press the button quickly with your thumb. A bat-style stick might feel better, at the expense of some precision, but I've never had one so I can't say for sure.