Decent ISP not as good as some suggest.
Biggest flaw and the reason I left them after 3-4 years they give out your personal details with ease.
If anyone contacts them they give out your personal details and in my opinion this is a valid reason never to be a customer.
Support is ok not great better knowledge than most but still pretty limited (by wage structure I assume).
Now I would consider it pretty dated ISP like Bethere.uk lagging way behind the competition. Zen never was going to be a major player which was the reason I joined in the first place.
As I now use my internet purely for mails and even that less so since mobile technology improved Sky is fine.
There are other ISP's that do not shape/manage out there. Zen tends to get a better write-up than they really merit.