The IRC bootstrapping method is deprecated and default off since the 0.6 release. It's still implemented and can be enabled using the -irc command line option.
The function of the IRC bootstrapping system will get replaced by DNS seeding and peer exchange, however.
The DNS system is vastly more scalable than an IRC channel. It has its downsides, in particular it is only unidirectional. However, given enough seeds it is much harder to knock out than a centralized IRC server.