If you are trying to pass it off as a SuperRep or plausible Gen from across the room-- then you will be disappointed with the 21J and synth-crystal IMHO. If you just want a fun, inexpensive watch and are not out to fool anyone, then it is a value.
Although the movement itself is fine, and easily R&R'd if there is a problem, the notchier sweep might bug you. Also, the lesser quality crystal won't 'pop'.
Here is a shot of my Swiss-Fish with the better sapphire crystal with AR.
Here is a white dial watch with a Synthethic crystal. (Note: less 'pop' and will look cloudy from the side)
HTH