I recently bought one of these Steam 420 PRO. This kit NEEDS a printed manual, the electronic can be printed at least.
It's a decent quality helicopter with most parts fitting really well (even the plastic parts). I do like that there are shims included for almost everything. Some people could say this is a issue with fit, but I've built high quality kits that could use shims to make the fit perfect. There are some clever things like a swash leveling and ball link tool. The ball links have a reinforcing ring Getting the boom aligned and installing the tail drive gear takes some patience. The landing gear with the metal inserts is kinda clever.
The Steam 420 blades are garbage. I mean they will be fine for hovering and sport flying, but you get what you pay for. If you are a hardcore 3D pilot, get a better set of 420s. The pinion also needs to be taller, getting a better feeling head speed needs a 13t pinion included in the kit.
Fly's well, but just needs a bit more "pop" which I think a better set of blades and a 13t pinion will wake it up a bit.