I was really disappointed with this kit, as I really like the Cybermen / Dalek figures in the range.
The moulding quality of the bricks is terrible - the edges are incredibly sharp and pointy, and could hurt a small child, while there are still mould marks where the bricks have been remove from their production sprues. Some of the design elements are questionable - the base is three 2x6 stud tiles, for example, instead of a more sensible 6x6, while the "roof" brick sits on four 2x4 tiles, when a deeper roof brick would have better. All of these together mean that, when assembled, you can still see the gaps between bricks, in a more obvious way than a Lego kit.
Like other people have said, the doors are fiddly and next to impossible to close without partial disassembly (Which makes the cardboard "TARDIS interior" piece a bit pointless), but a worse problem is that the four "frame" panels around the TARDIS aren't quite the same height as the support pillars, leaving a slight but noticeable gap at the top or bottom.
I haven't had the lantern fall off mine.
The Doctor figure is nice, but Amy just doesn't quite look right (The character design emphasises the lengths of people's faces, which doesn't work for her), and the way her hair has been designed makes moving her head difficult. Oh, and the top of the sonic screwdriver isn't green like in the illustration.
I know I'm probably not the target market, but this could have been a better toy than it ended up being. As it is, if your kids are Who fans, this is probably the best you're going to get; it's just that it feels like the second-best lego-y TARDIS kit, of the one available.