He liked it so much, he thinks it will kill third-party applications whose features the new Twitter subsumes, like Twitpic, which allows you to share photos on Twitter, and Twitter clients like Brizzly (mentioned above).
Twitter might just be among the first to take that path: it has has already spawned a vast number of third-party applications and web sites users tap into to interact with the service, such as Seesmic and Brizzly.