it really depends on where you are and where the transmitters are - its got a bit better over the years but even though I'm in a flat part of the country and about 10 miles from the Sandy Heath transmitter, DAB around here is poo either via car, portable or static DAB receiver.
with streaming apps for the smart phones, DAB is looking a bit shakey
*EDIT: please note that its not signal strength you are after, its signal quality