Hi Ross, the AZ-EQ5 is lighter weight and lighter duty than the HEQ5. The only issue I've seen with the AZ-EQ5 is that the worm mesh needs adjusting, but that goes for most new Skywatcher mounts.
If you're not confident in adjusting worm mesh you can get it done by Skywatcher Australia under warranty, assuming there is a little backlash in your mount. The main thing to avoid is having the worms too tight causing binding.
Here are some instructions on how to adjust the worm gears on the AZ-EQ5:
http://www.astronomo.org/foro/index.php?topic=17215.120
Basically the motor cover and motor is removed, then the mesh is adjusted and you do a full 360 degree rotation looking for binding.
The EQ6 family of mounts are simpler to adjust but probably equally finicky in terms of getting the adjustment just right.