I'll add that I had (actually still have) and LCD Top Gun II that I used for a while on my stand up cab.
It worked OK, but I had to stand back from the screen/IR LEDs about 4-5 feet, which was far less than ideal for a stand up cab with a 21" monitor.
If you are using a showcase style cab, or just run it off a large TV where you can stand back a ways, it works fine.
Some people modified the lens on the gun to one with a wider angle that helped some.
The Aimtraks are supposed to be better, allowing you to get 2-3ft back. And the Aimtraks are probably much easier to get working since they appear as a regular mouse. No drivers to fiddle with.
But if you are hoping to duplicate the experience of playing Duck Hunt or Hogan's Alley on a standup cab, you likely will be disappointed since you can't belly up to the CP and blast away.