I would like to add an option/preference to disable IRC in the client. It should be on by default, since that's the whole point, to bootstrap new users, but then the user should be able to switch it off. There will still be plenty of people who leave it on to provide booting to others, but not everyone needs to do that; especially if you don't have the inbound port open.
-noirc...done
I also think that alternative bootstrap methods are a good idea, but it should be possible to switch it all off once you're connected to the network.
That already pretty much happens, bitcoin prefers nodes it has previously connected to, so as long as it has made a decent number of connections in the past it shouldn't bother with nodes from bootstrap sources. Plus keep in mind bootstrap sources are just lists of IPs, which is really no different from what you get via peer exchange.