My Jetfire arrived, and I've been messing with it a bit. He feels very solid overall, although some joints are slightly loose on mine. The chest panels easily open up. The robot mode is excellent and it's going to be hard to decide between the armoured mode or the regular one. Jet mode is great unless you look under it. Functionality is phenomenal with all the hooks for smaller characters to hang on to, two cockpits for Titanmasters and neat stuff like the rocket flare effects and the changing Autobot logo. I also like the subtle grey paint on the legs and the nose of the jet, rather than the sloppy dirt effect they have on most Siege figures.
The only real issue for me is that he's a bit big - I tend to prefer when big characters are only slightly taller than the rest. This guy towers over everyone except the combiners. I guess he's to scale with Blaster at least.