Unless you are moving to a nearby area, I wouldn't expect to get your security deposit back. The apartment complex likely has a lawyer or collection company working with them that will appear and court and ask for a default judgment.

You personally made a huge mistake when you left in not doing a walk-through. If you do not do a walk through it will be your word vs. the landlords in the condition of the apartment. They will likely have actual receipts for repairs or cleanup which will be likely carry the day in court. As far as shampooing a carpet, I would think you would need to have the carpet professionally steam cleaned. Most leases specifically require a professional to clean to the carpets when you move out. As a prospective tenant, I would require the carpet to be professionally cleaned prior to moving in.

If you lived in an apartment for 3 years, I would expect that you clearly had in excess of $200 in damages. Damaged outlets, paint scratches, carpet stains, cracks in tile, holes in walls, and general professional cleaning and carpet cleaning would normally cost well over $100. I understand that you feel that most of the damage was "normal wear and tear" however, a Judge could rule otherwise.

If you live nearby and don't mind going to court a few times, by all means go to court to resolve the dispute. If you are moving any considerable distance, and you may miss work by going to court, it may be in your best interest just to pay.

I'd recommend you pay it. Consulting with a lawyer will be more expensive than if you were to pay the extra $100+. You do not have much of a defense to stand on unless you took pictures of the apartment from when you moved in and again when you moved out.