For me (East Midlands region) the gas is marginally cheaper than the eon MSE collective tariff (2.756p vs 2.859p) and the electricity is marginally more expensive (9.979p vs 9.450p) standing charges, discounts and exit fees unchanged.
Obviously it depends on your gas/electric mix whether it's overall positive or negative, for me based on previous 12 month actual usage, it's theoretically £8 cheaper, barely worthwhile but I could set switch date as far into future as they allow to effectively extend my fix by six months.
Might be useful for anyone who didn't get onto their MSE tariff back in September.