I joined on a 12 month contract in December (unlimited calls, unlimited texts, 3 GB data, for £15.00/month {but charging £3.99 for first 3 months}).
They use the EE network for connection, and while I've had a minor glitch (they managed to list calls I made as chargeable, on the invoice, and once I complained, they acknowledged they should not have been charged for, and cancelled the cost... very easy), I am still happy to recommend them.
I am about to move one of my other numbers over to them (to replace the number they issued with the SIM), only to reduce confusion from friends and business contacts, but see their deal as good value.
I suppose the question is whether the package at £10 meets your needs - that seems a very good bundle (and I know they've temporarily made the £15 cost just £10) but for some people who use more data (600-1000, say), then something like the Three "3-2-1" PAYG deal might be worth looking at, too (1p per MB of data, 2p per text, or 3p per minute for calls).