Well as someone who used it for nearly 2 years (I don't use it anymore, thank gosh). It's okay for beginners, but once you try doing some advanced stuff or making animations longer than a minute, that's when the program starts to show it's true flaws, especially the free version which I used.
An animation I made on here called Squash the Ball (which was animated 12 fps but runs at 14 so it could play faster) could've taken me a day or 2 if I would've made it in Flash, but since I made in Flipaclip, it took me nearly 2 weeks to make because I had to draw the ball every single frame, I had to use straight ahead animation because it's nearly impossible to keyframe, the program would lag after a certain amount of frames drawn, no vcam so I had to redraw the background multiple times for a moving shot, and there is no tweening so I had to manually move objects frame by frame which was a total pain. In retrospect, the animation still turn out to be terrible anyway.
In conclusion, I only recommend this program to an absolute beginner in animation. Anyone that plans on making fully length animations should stay away from this program. It was made for beginners in mind anyway.
Edit: Oh and I forgot to mention that disgusting watermark. It literally can make animation go from a 7/10 to a 3l10. It looks so unprofessional.