They're very good cars.

The only "complete" car to come out of the BMW/Rover tie up (the 75/ZT) and it was excellent.

The swift disappearance of MG Rover hit prices hard, although the ZT260's still fetch relatively strong money.

For the cash they're a great car and there really is no "catch". To be fair, a similarly-aged Mondeo ST220 doesn't cost all that much more in realisty, so for a 7-9 year old V6 sporting saloon the price isn't really that stupidly low, but it still represents a lot of car for the money.