Yes, I have similar experiences with Vodafone. I signed up for a 2 year deal at £15 per month but, when I started, I ordered over the interenet so that, if coverage wasn't up to scratch, I could cancel under the distance selling regulations. But I've been quite pleased overall. A while ago their servers couldn't manage to send more than about one email in five which was very annoying but I swapped a few messages with their customer support people and the issue seems to be resolved now.

It is frustrating when there's a bad connection but it's not all that bad if you are old enough to remember when 56k modems were hot property. I have found that having the dongle on a cable and moving it around can sometimes improve the connection.