The negatives? Their back-lot version of French colonial Casablanca doesn't look much like today's Casablanca. Of course 1942 Hollywood didn't look much like today's Hollywood, either.
Another negative, and a more substantial one, is the left-wing bias in the dialog and script. Bogie's character, Rick, is described as having run guns to the Ethiopians and fought on the side of the left-wing loyalists in Spain. The Paul Henried character, Victor Lazlo, is pretty clearly a lefty too. You could conclude that Rick had become a neo-con, a lefty who had been mugged by reality. That is, until Lazlo pulls him back into "the cause."
The cause is never explained and you are encouraged to view it as simply anti-Nazi, except that by the time the film was made in 1942 the German invasion of Russia had already occurred. It is relatively clear that "the cause" was in fact Communism which, after a flirtation with the Nazis during the two years of the Molotov-Ribbentrop Pact, became anti-Nazi as well.
Films like this probably triggered Sen. McCarthy's Communist-hunt through Hollywood. Casablanca and films like it show there was "smoke" and his search for "fire" was not irrational.
It is still a lot of fun, with a lot of great lines, some humor, and a sad love story in a time of war.
