It is the exact same vinyl that Cricut sells. If you look on the back of your vinyl, it says Oracal 631. This vinyl is also Oracal 631. The only difference is that this is sold in larger rolls: either 24" wide, or 15" wide (with perforated edges). I think you have to buy it either in 15 foot or 50 foot lengths. But if you use it a lot, or go in on it with friends, it is a great deal.
I thought their service was great, and the shipping cost was good (at least to where I live) if you buy your rolls all at once. They can also give you a folder with color charts in it for future ordering. They gave me mine free with my order. You might have to pay for it if you aren't ordering yet, I don't know.
They also sell permanent vinyl, which is weather proof and should last 3-5 years, depending on which you buy. For that type, you need a special removing fluid to get the vinyl off (use only on places like glass or on a banner, never on your walls). When I bought a banner to put it on, I also bought a special fluid that gave me extra time to reposition the vinyl, in case I made a mistake when I laid it down.
The cost of the vinyl, if I remember correctly, averaged 66 cents per square foot. A great deal when compared to the $2.50 per square foot that you pay when you buy it in the sheets sold in clear boxes at craft stores. I haven't seen anywhere online cheaper.