They don't work at all well in poor reception areas; or, at least, not without upgrading the roof aerial.

In some transmitter areas, including the Sandy Heath transmitter which serves Cambridge, roof-aerial replacement is basically unavoidable, as the analogue channels were all closely grouped together in frequency, so most houses had narrow-band aerials installed. But the replacement digital channels are all over the (relevant part of the) spectrum, requiring a wide-band aerial.

Peter