I also have the Solvit Tagalong Booster seats and very happy with the purchase. Zoey doesn't get carsick (at least none that I have noticed) but I always felt bad that she couldn't see out the window too well with her being so... short.
There were few reasons I chose this one over the snoozer (another very good booster). To name one, it's collapsible so I can easily put it away if needed and doesn't take up much space. The price is really good for the quality. The only thing I would advise is that you choose the size of the seat depending on Crystal's size (not weight). Zoey's very small. About 9" when standing, maybe 11" long... I got her the medium and she has enough room to move around and be comfortable.
Please post a pic of her on her new ride when she gets it!