I used this to help my dog on a long car trip. It worked great. Once it kicked in, she was very calm and it didn't make her sick or anything. Tried a half day without it on the way back, and there was a clear difference.
However you don't need as much as they say. My dog is about 40 lbs and it said to give her 2 an hour before and then 2 right before. I only gave her one each time, and that was plenty.

Pros: works great for travel

Cons: you don't need as much as they tell you

This was great. My dog always gets carsick when we travel. He manages to go around town fine but anytime we hit curvy roads he throws up. My vets office recommended this product recently so I tried it. I have now taken two trips with my dog with absolutely no illness on his part. It does not make him calm (He is pretty crazy) but it does allow him to enjoy traveling without being sick. My only suggestion is it is not enticing for the dog to eat. It is something that he has to be forced to eat. If you use it wrap it in something tasty.

Pros: No Throwing up

Cons: Not enticing to take