The Tornados' achievement at the begining of GW1 comes to my mind as an exemple. The Gripen and Typhons hiccup when they were first engaged in Libya is an other. The combat proven label isn't just about what the aircraft could do, it is more about the objective evaluation of its actual limitations in a real war and knowing how to use the whole system to overcome those limitations or/and financing relevant upgrades to correct them in the future.
To be fair, I could also give the exemple of the first Rafale deployements in Afghanistan. What was learned about the aircraft during these low intensity war missions was priceless and certainly helped a lot to speed up the maturation of the systems and people using them.