Well my son has quite a few cobi models now and this is one I wanted to get him for a while, mainly because it's been 50% off rrp for as long as I've known.
You get 500 pieces which for the price is amazing ,and its split between the 3 models and a tree! Firstly the jeep is easy to build and has good instructions and is slightly bigger than those 60 piece jeeps/cars that cobi sell.
The plane has bad instructions and wasn't an easy build, although when built it was quite sturdy .The main bad point is that the canopy doesn't fit flush with the cockpit.Also the block that holds the rockets on is better under the wing rather than on top as it makes it more stable!
The tank was a build and a half ,the instructions were passable and the main bit of the tank was quite easy to build. Beware.. make sure you have double checked the bottom part before you fit on the top part as any mistakes will involve taking it apart later when not so easy. The tank itself is about 9" long without the gun and 11" with gun.
The tracks do work quite well but don't expect mega speeds, the turret also works quite well and rotates round smoothly.
The only downside to the tank is that they added too much overhanging the sides, which I promptly removed about half of. The overhang at the back of the turet also looks messy but I have left that on for the minute. You can have two men standing in the tank but the one in the drivers positon will get a sore head as the gun keeps knocking him as it traverses, my son finds it funny though.
You get 5 men in total with a pilot and a tankcrew man, and an officer with 2 soldiers. No extra weapons for them but its not a major loss.
So to let my 4 year old play with them I stripped down all the rubbish off the outside of the tank and had no problems so far, the jeep has a weak bit at the back where the lights fall off when played rough with, but I will sort that out with an extra block later on. And the plane is surprisingly sturdy with the rockets being quite hard for him to take off and no other bits have come off yet.
Hope this helps