[Brys]

I thought that the ending to Perdido Street Station (my favourite of his novels) was his weakest, while the Scar's endings and especially Iron Council's were decent. The Scar had a very dark, postmodern style ending that I think fits particularly well with Mieville's general style of anti-fantasy - very much what you would expect in an M John Harrison novel, or a Peake novel. Iron Council was even more this - typical of Mieville, focusing on how everything doesn't turn out right, that despite best intentions, things do go wrong.
The revelations of Yagharek at the end of Perdido were brilliant, the deus ex machina of Jack Half-a-Prayer, less so.