Don't take the following points the wrong way, I like the 600 a lot, it's still one of my favourite helis despite having more 'exotic' helis in my fleet. ... But focussing on the things that sometimes get criticised:
- Low tail gear ratio meaning that tail hold is weak unless you run screaming headspeed
- Tail drive bevel gears stripping
'1' is really due to the 'design intent' of the heli. Align made the Pro as a hardcore 3D heli intended to run very high headspeed, so it's not really a fault as such. But for those of us who like to have slightly longer flights at less manic headspeeds it is an issue. You can fix by fitting the older generation mod 0.6 auto gear and tail drive gear set which speeds up the tail, or you could fit the new three blade tail. You can also fit larger tail blades but to do that you should do a 'stretch' because there isn't enough clearance so blade clash is possible.
'2' can largely be fixed by either running very low gain on the CC governor, or by using a different brand ESC. Also the bevel gears often need to be shimmed to make their mesh as tight as can be without binding.
The other minor annoyance I found is that with the low profile landing gear the tail is too low and the blades easily dig the dirt. The best fix for this is to get a set on landing gear from the new Trex 700X or 550X which are raked to give a nose down/tail up stance. The other criticism some might throw at it is that it's a bit on the heavy side for a 600, but as long as you run reasonable headspeed that's not too much of an issue. It's actually a great flying heli
