Acrylic is something like 10x stronger than glass and also clearer when it is new. Of course the drawback is the easy scratching (I have a used one with infinitessimal little marks all over the tank from the teeth of a pleco) but this is not as apparent when the tank is full. Minor scratches can be removed either by sanding or by a polish such as Novus Acrylic Polish and Scratch Remover.
Scratching will also result if you use a pot-srubber or razor to remove algae, ro if th esubstrate is ground against the tank wall while you are vacuuming. I have had success scrubbing algae off mine with a toothbrush and there ar ealso a number of commercially available 'acrylic-safe' algae removing tools.
Many acrylic tanks are mostly seamless and paired with their resistance to breaking it makes the tank very strong, a definite plus if you are, say, a college kid like myself faced with the threat of drunk friends careening into the tank or moving apartments on a yearly basis. Furthermore they are popular with monster keepers again for their suitability for 'tank busters' and also because glass tanks of more than a few hundered gallone are rather rare.
So in conclusion acrylic tanks are definitely function over form and if you are looking for a good, cheap durable tank acrylic is the stuff for you.