I certainly wouldn't go against Greysts view but I can only speak as I find.
My Vodafone dongle performs very adequately when I am out and about. I drive into Derbyshire quite regularly and have received a usable signal miles from anywhere. At home I am a Virgin cable user so about that aspect I cannot speak.
As
Vodafone say in the link, it's £15 per month (
a few pence cheaper now since VAT change) which has saved me lots on Wi-Fi hotspots.
.