I've found the Emerald Aisle at this location pretty thin the last few times I've used it. That said, I've generally gotten something that I like anyway. Last visit I grabbed a Prius in the Aisle fresh from the car wash. They seem to have a bigger variety of cars than other National locations, which can be very heavy on the American models.
Service is quick and efficient. Prices are competitive.
The only downside is that the CLE rental car facility is horribly inconvenient from the terminal. That's not the fault of National (or any rental company) but you need to add at least 10 minutes for pick-up and drop-off as a result.