I'd be wary of a door-to-door salesman's pitch; If you want to look for cheaper bills then your better off (I think) using a website like Uswitch.com - there you can put in your supplier, tariff & how much you use then it gives you a list of cheaper products.
As an aside:
There was a chap on radio 4 yesterday saying that as Scottish power are putting up their prices it would be good to grab a 'fixed price' tariff before next week, as the other companies are probably going to follow suit very soon.
only thing I can say about eon is that it took me five phonecalls to get a consistent answer as to how my existing tariff worked, another three to get them to admit they had a better one for me and transfer me onto it; then 3 weeks after going onto the new tariff they changed it
. I don't know if that's any worse than any other company though.
m