Things I liked: Height, solid construction, dual bolt clamps to rail, reasonable price.
Things I would have changed: Coated interior surface to reduce marring of scope, bigger see through channel, as I still cannot gain bead with open sights. Easily scratched, so maybe a better coating process? Minor issues.
What others should know: Better than weaver junk, strong enough for C02 guns. Can't speak to use on springers, although they provide a pin for use in conjunction with stop.
Things I liked: Great power & accuracy, easy to fill with pump or scuba tank. Nice walnut stock, great fiber optic sights (but the rear could be improved - see comment below). Dual fuel option capability is a bonus. This is an incredible rifle for the money.
Things I would have changed: Rear sight should have finger adjustments like the QB finger adjust rear, but an easy an inexpensive swap. Shrouded barrel to make it more neighbor friendly, this thing is LOUD.
What others should know: If you are looking to get into PCP rifles, this is a great starting point. Competition and hunt ready out of the box if you have a way to fill it. Replacement, fill and mod parts are abundant for low cost. Don't hesitate, buy it - you won't regret it.