One change about this that I like is that the markup is a blockquote, not a div. Blockquote is really the more semantic of the two for a tweet: you’re quoting somebody and if your styling fails it will display indented like all other blockquotes.
Unfortunately, shortcodes do not currently work for WordPress.org sites like this one. Jetpack was supposedly going to bring feature parity with WordPress.com, so maybe it’ll appear soon. In the meantime, there’s Blackbird Pie.
And for those of you on WordPress.com, here’s how they do Twitter embeds.