I used to hate using a joystick on my Amiga for platform games and having to push up to jump so I wired one of the GX400 pads so that button 2 was linked to the 'up' of the D-pad.
I whooped Superfrog using that joypad! It had a very similar feel to the 8 bit nintendo joypad but had rounded edges and was surprisingly good in use.
The actual GX400 was a total flop (mine was given to me after it turned up at a jumble sale) - No games except the built in game Burning Rubber (average).
I still love my CPC though! The one machine Amstrad actually got right.