Frankfurt Airport is one of the largest and busiest airports in Europe, and overall I've had mostly…read morepositive experiences here. The facilities are modern, clean, and there are plenty of shops, restaurants, and places to sit while waiting for a flight.
The biggest downside is the walking. Depending on your gate and connection, transfer routes can be surprisingly long. I've had a few tight connections where it felt like I was speed-walking across half the airport. If you're connecting through Frankfurt, give yourself some extra time if possible.
That said, signage is generally clear, security and passport control have been reasonably efficient in my experience, and the airport handles a huge volume of passengers remarkably well. It may not be the most relaxing airport for a connection, but it's organized, functional, and gets the job done.
A solid international hub overall--just be prepared for a bit of exercise between flights.
My fitness tracker probably loves Frankfurt Airport more than I do!!