Right, got my Q5 C2 today, had a play around with it, and I am impressed. It's got a warmer tint to the original C2, and what looks like a 20% brightness increase in dark, wet and misty conditions. ( Winter in the UK, lovely). White wall bounces show the difference nicely, but the tint really seems to help with colour rendition outdoors. This is purely a personal viewpoint, scientific evidence may point to the contrary.
Otherwise, finish is nice, a bit smoother than my original C2, I only have the HAII finish one, so can't compare with the HAIII. The bodies appear to be identical, so you should be able to transplant the innards across to a HAIII body if you are so inclined.
It's not a huge leap up from the original C2 in any way, just a gradual improvement, but it's a damn fine light.
Delivery time was just under 2 weeks from China to the UK, although actual transit time was only 4 days from order despatch.
If you mean to use this with the Bike mounting clamp from DX, be prepared to heavily modify the attachments, the clamp is a nice idea, but let down by poor execution. I had to replace one of the bolts, reshape the area where the flashlight sits, and use 2 small Neodymium magnets to ensure the clamp locks securely.