Yes Leo, if the offer seems too good to be true then it simply isn't true. I notice on the PPP website they don't quote rates or do comparisons with other providers on a rates or total costs basis. I'm sure they have a role to play in the marketplace (e.g. rental properties) but for Séan or Sheila Citizen, I don't think they compete, certainly not on price as in my case.
The other issue to be borne in mind is that if you get free electricity units as part of your SW entitlement, switching to a supplier other than EI will leave you cash flow negative. In other words, you will be paying full electricity bills and have money refunded to you after the bill is paid in full. EI is very convenient as you pay the reduced bill.