This tire rating thing is getting a little out of hand, but since we live in such a litigious country, the tire guy was just trying to cover his posterior. Plus the Vibe is such a high performance car, that H speed rating is necessary!! Just kidding
Note the limits for your tires. Most people don't consider any type of rating on a tire. Weight (load rating) and Speed are two of the big ones that really count. Inform yourself, but use reasonable judgement. There are some pretty poor tires out there to watch out for and can be easily researched on the internet.
If you buy a tire, you can always check the ratings on the sidewalls. Lot's of info on there... UTQG (Uniform Tire Quality Grading) info. Even the date of manufacture is there. That's really important. Most tires will start to show very small cosmetic "Cracks" in the rubber at around 6 years of age. The cracks are an indications that the tire is coming to the end of it's life.
The tire is one of the most critical systems on your car. Inflate them properly and check their condition every couple of weeks. Never
over inflate... the max cold tire PSI is also found on the tire sidewal
l. Drive reasonably and don't overload the car. Hot summer weather and fast travel with vacation loads can wreak havoc on tires that are not properly maintained.
Cooper makes excellent tires and is still an American company.