I pay £110 per year, for as many deliveries as I want, provided they are £40 or more in value. It also gives first dibs on Christmas deliveries, but the delivery charge on these is extra.
In fact, I get two deliveries each week. Is is very convenient, because it is rare that I have to pop to a supermarket for forgotten items, or for something that hasn't a week.
They do a price match with Tesco, so that if the shopping is more, you get a voucher for the difference. This week, for example, I saved £1.22 compared to Tesco, so I don't get a voucher.
I used to use the MySupermarket.com website, where you could compare items directly between sainsburys, Tesco, Asda and Ocado. Often, the item I wanted to buy was not even available at other supermarkets.
There are hour time slots, and at busy times, ese are half an hour apart, so you could choose between 4 and 5, or 4:30 and 5:30, say.
The drivers are polite, and rarely late (although Friday nights are often problematic - avoid them if you can). There is never any difficulty getting a refund if an item is damaged.
The iPad and iPhone apps are really easy to use.
So, you get an excellent service, and it's not more expensive than the big supermarkets. (More than Aldi, but they don't deliver.)