What it says in the description!
£35 per month outlay, but with 7 months cashback (on redemption) and £40 QC, works out £11.25pm. With a 4gb card to boot. Doesn't seem that bad to me. Even without the QC it comes in at less than £15pm.
Avoid if you don't like cashback redemptions. (I've been stung once when CoolNewMobiles went to the wall, but this is backed by CarphoneWarehouse so a much safer risk).
Don't seem to be able to link to the deal direct, so select 12months Vodafone deals - it should be the top one. Don't be tempted by the 12months at 1/2 price ... doesn't work out as cheap!