I have 5 of these bags in various colours. I started with one as part of an earth day pledge and used it all the time so I bought more. Since they pack so small, they are easy to leave in the car or your pocket which means they get used all the time. The problem I found with other reusable bags is the bulk which means I kept forgetting to take them with me to the store.
I also have a bunch of cheapo bags which are modeled after conventional shopping bags but they never get used because they cut into the hand when carrying. The over shoulder design of this bag is great.
The only downside is that it's a little small so I'd need to have 10 for a trolley full of shopping which is probably the same as you would need in regular plastic bags. It would be nice if they made a larger one.
And must thank zenful83 for their review which introduced this bag to me!