I'm a bit late catching up with this film, and wondered if I could enjoy it having seen/heard so many clips + quotes over the years. The answer is "yes"!
Even though everyone on the planet must have had the ending spoilered for them by now, the film still delivers entertainment and quality in spades. The script is deliciously witty and full of drama, the characters wonderfully crafted and 3-dimensional, the cinematography and sound as classy as anything in its day.
It's fascinating to compare a film like Casablanca to the dross Hollywood produces these days... so much more money, technology and every other resource available, and they can't produce anything remotely as good!