I have, in the course of my life, probably seen ravens before. But since I've been birdwatching, I've been living in a section of the US pretty light on the raven population, and so, I hadn't ever counted one, or paid particular attention to one.
After all, they were just big crows, right? Quite large crows, crows with beards, crows on steroids possibly, but still basically just a big crow.
Having now seen ravens, I can safely say that if it's a crow, it's an epic crow. An end-boss crow. A crow that one might expect to see rampaging through downtown Tokyo, smashing buildings under its scaly feet while thousands of tiny people run in all directions, occasionally looking over their shoulders to scream "Crowjira!" and faint.
Ravens are bloody HUGE. Poe must have had enormous windows and the bust of Pallas above his chamber door must have been in heroic sculptural proportion. Those things could eat small children, and they look like they're thinking about it.
My new rule of thumb for corvid identification: "If you're wondering if it's a crow, it is. If it's a raven, you're wondering if it's an airplane." (This joins other rules of thumb such as "any raptor is a red-tailed hawk until proven otherwise," and "do not bother with the small brown sparrows unless they are sitting right in front of you and you have time to get out the Sibley and look back and forth for ten minutes.")