(at around 16 mins) The passage that Jesse cites, which tipped her off about Lestat being a real vampire, is not actually part of the song used in the film.
(at around 23 mins) Marius cuts his arm so that Lestat will drink his blood. Clearly, there is blood dripping from Marius' arm as Lestat drinks. When Marius pulls his arm away Lestat does not have blood on his face but he should have. Moments later Lestat has a small trace of blood under his chin.
(at around 1h 35 mins) At the end, when Jesse and Lestat are walking out of the Talamasca, they switch places between shots.
During their walk in the park, the cut above Jesse's right breast keeps appearing and disappearing.
In the movie, it shows that Marius was the creator of LeStat. However in "The Vampire Chronicles" books the creator of LeStat was Magnus. Still, viewers should remember that when a work of fiction is adapted from one medium to another, details are routinely changed in order to fit the style of the new medium. Therefore, what holds true in the "universe" of the Vampire Chronicles books doesn't automatically have to hold true in the Vampire Chronicles movies.
(at around 23 mins) Before Lestat takes his 'first' drink from Marius, while the blood (or whatever makeup or drink they used) is dripping on his chin, Lestat opens his mouth. When he does this you can clearly see that his mouth is already full of blood (or juice).
(at around 28 mins) When the gypsy girl is lying dead on the pyre, you can see the pulse at the base of her neck.
After Lestat snaps Sophia's neck (the Greek/Gypsy girl playing the violin on the beach), you clearly see her smile as he lowers her to the ground.
(at around 53 mins) When the Queen pulls the heart of the guy that is in the club right before she takes a bite out of it you can see that it's beating, A vampire's heart would be dead and not beating.
(at around 14 mins) The girl playing young Jesse has bright blue-grayish eyes, but older Jesse seemingly has brown eyes.
(at around 38 mins) While in the vampire bar, the woman playing the drums is not playing the same song, or the same rhythm.
(at around 1h 35 mins) When Marius visits David, you can see someone cueing Marius to say, "Hello, David" reflected in the glass curio case on the shelf behind David (to the right of the screen).
(at around 1h 7 mins) Shadow of the wire-cam visible on the front-drop of the stage (right of screen) during the overhead zoom into Lestat during the concert.