I bought one of these seats so that we didn't have to keep transferring car seats from my car to my husband's. We chose this seat as it is suitable from 9 months to about 11 years. It can be converted from a car seat to a booster seat for an older child by removing the back. It is also easier to transfer when grandparents etc want to take your child out. Your child is fastened in with the normal adult seatbelt, which is put through a clip just above their shoulder. The cover is machine washable.
The problem that I have though is that my 3 1/2 year old daughter can climb out very easily unlike with our Freeway Excel - the last time it was when I was driving on the motorway and she appeared in the front of the car!
The good thing though is that we will not need to buy a separate booster seat for the car when she gets too big for her car seat.