Mobile Viking

I do. Coverage is fine in Belgium (though can vanish sometimes when you're out in the country as you might expect. Have also used it in UK and Milan and France (well, on the Eurostar). Never had a problem. When abroad it will just pick ip a local network - Orange in France and Vodafone in UK usually. I guess you can scan for available networks but I never bother. And obviously you need to watch for roaming charges when abroad.
In Brussels I get a solid 3G signal on it - regularly listen to internet radio on my iPhone using it, so yes, it's fairly reliable in my experience.