1) DURABLE. They will scratch a little from time to time, and dent slightly, but they really are tanks and will withstand almost anything short of being hit with a fireman's axe.
2) Very resistant to wear and tear. They will wear over time and use, scratch and dent slightly if dropped (they are aluminum), but are INCREDIBLY durable and can take punishment that would likely shred your typical store bought Hasbro FXs.
3) Depends on the batteries, but I understand the recommended lith Ions will last about an hour, maybe 2. I have some rechargable Energizers that last a good long while, though the blade does dim somewhat as they start to die. Not very badly though.
4) I'd rate Obsidian's volume about a 3.5 to 4. It's loud enough that you can use it outside (near a freeway no less!) and still hear it, but you can turn it on and still talk to your opponent without raising your voice. AKA, you turn it on in your room while someone is watching TV in the living room, odds are you won't really be bugging them TOO much.
5)Pretty accurate to your swings and hits, and it is easily adjustable on your computer to fit your personal preferences.
6) I'd just use a little windex or pledge on a rag and wipe em' down, but I'd never really actually had to clean mine. Plus I like the slightly dirty look as it makes them feel more real to me.