I've been using Tesco Momentum 99 for over two years now, it's my preferred choice of super unleaded and the benefits are: cheapest super on the market; improved economy; and the more you spend at Tesco the more rewards you'll get with them, eg vouchers to pay for fuel, clubcard points etc.
Personally, I don't see much difference between V-Power, Ultimate and Momentum 99. But I do want to try Sainsburys Super and was wondering if it's the same stuff as BP's Ultimate cos of the Nectar card connection; the Sainsburys garage near me was charging 1.32p/litre for its Super but that was the price six weeks ago! Likely to have gone up.