I bought this a week ago on a shopping trip to Tescos, part of a binge in seeing new TFs on the UK shelves.
The concept here is that the Star Wars vehicles are Transformers who turn into robots that resemble the original character. The vehicles come with a pilot of the actual character.
Darth Vader (Toy's) Vehicle Mode is Darth Vader (character's) Tie Fighter - the one he uses in the climax of Star Wars. The ship is about the same size as the old action fleet version - 12 1/2 cm * 11 cm * 8 cm. From the front and the top it looks a reasonable replica. There's a pair of missile launchers under the wings that take 2 lightsabre shaped missiles. The missile launchers will not fire on mine. Underneath is a mess - lots of identifiable Vader chest. The wing on the left of the vehicle (looking towards it, it's right) has some hinges in it. If the pieces these are connected to aren't locked together just right the wing will collapse. The pilot will fit in the cockpit. But only just, and he's sitting in an odd position.
To TF remove both wings. Place the underside towards you and pull the missile launchers to the sides to form the wings. When I did this initially and one of the missile launchers - which forms the forearms - fell off, I knew I wasn't onto a winner with this toy. The hands slide out of the forearms. Fold the lower panels on his back back in on themselves and pull on the sides of the fighter body to fold his legs out. Swivel at the knees and extend the feet. Open the cockpit up, fold out the head and lock into place. The solid wing forms a shield that clips into one arm, the hinged wing is a cloak, and the missiles are his lightsabres. And there you have it.
The robot looks odd. The main body does a fair impersonation of Darth Vader, even though it looks misproportioned in the upper body and oddly posed in the arms. It's spoilt slightly by blue grey in the feet / chest sides and spoilt loads by the tie wing hanging of his arm and back. The hinged sections on the cloak add nothing to the toy - his posability in his legs is limited by the top of the TIE body being behind them - thus rendering them meaningless and by virtue of destabilising the vehicle mode a minus point on the toy as a whole. The lightsabres are not keen to stay in his hands which fails them as both hand missiles and weapons
Attempts to pose him other than standing vertically have proved difficult. He's jointed at the knee - lower leg bends backwards - with a swivel joint above it. His hip is an obscured universal joint - IT IS NOT A BALL JOINT, A BALL JOINT INVOLVES A BALL IN THE JOINT SEE BEAST WARS TOYS ! Glad to get that one off my chest ! Shoulders move fore and aft but are limited by the top of the cloak. Arms move to the side inside the shoulders and just below, yet there is no bicep joint. Elbow bends in the plane of his arm movement , and there's a swivel below the elbow - where the missile launcher detached on original TF - and at the wrist. Head movement is limited from side to side, but limited at about normal human range so that's OK.
Overall: Well I thought the entire Star Wars Transformers thing was a bad idea from the start and this is especially poor execution. It can't decide if the robot is meant to be Darth Vader or not, and in doing so has compromised both modes with stuff from the other. It may have been improved by casting the entire starfighter in black ! And to be honest this is what the entire line suffers from - although the vehicle modes all look fine from one angle, there's frequently something robot visible somewhere because the robot has to at least make you think of the character, and all the robots suffer outrageously from kibble. Vader at least looks like Vader, I'm not sure if Obi wan or Luke have more than a remote resemblance. If it were a normal TF we'd be slagging it off, and I see no reason to treat it differently.