While CLE might not be as busy as it used to be when it was one of only 3 hubs for Continental Airlines (which has since merged with United and deemphasized CLE greatly), it's a somewhat large airport for a city of Cleveland's size while not being so large as to be bewildering. It offers a decent array of concessions, is pretty easy to navigate, and is fairly painless when it comes to checking in, clearing security, or picking up bags at baggage claim.
Parking lots and a subway station that whisks you into downtown in minutes are an easy walk from the terminal, so you can literally scoot right up to the airport and jump on a flight quickly no matter how you're getting here. Rental cars are located offsite, however, so budget in plenty of time when returning to the airport.