Since everyone on this thread is such a good diver that they shouldn't be bothered with questions or a checkout dive, I'll raise my hand as the opposite. I had an AOW and Rescue card, which I used to board a boat requiring an "advanced diver certification". I even had obtained a dry suit card and the experience of a couple shore dives in cold water, since my certification classes were in the tropics. I was still woefully ill prepared.
I had used a compass during my AOW training in clear blue Caribbean water. But that didn't mean I could navigate low vis cold surgy green water. I had never lead a dive. I had never planned a dive. Gas plan was to return to the boat with 500 psi (in other words, we didn't have one). My buddy was struggling, using gas quickly, and a few minutes into the dive he flashed his SPG at me which read 800 psi. We were 90' deep and not close to the anchor line. I was worried. I knew he didn't have enough gas to make it back to the boat, and I didn't know how to launch the DSMB I was carrying (lot of good that did). We made a free ascent, and we lost each other on the way up, because it took my entire mental capacity to watch my computer and manage my drysuit. We surfaced a good distance down current from the boat, but thankfully reunited we were able to swim back unharmed. I'm lucky nothing really bad happened, but it was a scary experience which taught me a valuable lesson. My AOW card didn't mean I could (or should) do this dive, and my rescue card did not mean I had the capacity to help my buddy if he was in trouble.
It prompted me to seek out more training with an instructor who not only taught the skills but insisted on repetitive practice until they were done well. And done well again. And again. He didn't hesitate to withhold a cert card from a diver who didn't meet standards. He offered critical feedback and the class was definitely no vacation - it was hard. But it made me a better diver. The next time I went out on that boat was in much worse conditions, but this time I was adequately prepared. AOW wasn't nearly enough to get me there. And I'm sure I'm not the only one.