Warnock seems to be becoming a better manager with age. He was already a good one but now is correcting mistakes each time he starts at a new club:
i) did a good job with Rotherham but left before able to complete their turn around
ii) stayed longer with Cardiff to complete turn around, but thought far too much about the short-term and spent far too much money taking us back to where we were before he arrived
iii) Completing the turn around with Boro, is now talking about longer term plans for the club and doesn't seem to have spent so poorly thus far.
From what I can see, one of the biggest criticism of him as a manager from his old clubs is that he leaves clubs up a creek having spent big on limited and/or older players. He did that here which is why he's got such a bad reputation.