I just bought the 10w power adapter this morning. This thing is totally worth the 30 bucks I payed for it. Its always nice to have an extra wall plug and sync cable.
Yes - it's good to have a few spare adaptors. I keep one at work and one at home, to save keep having to unplug and box up the one adaptor. The battery life of the iPad is more than enough to cope with the commute.
Between my wife and I, we have seven iPod/iPhone/iPad chargers - more than enough to outfit multiple points at home and in the office (since we're usually in no hurry to charge.)