get_template_directory() vs bloginfo( 'template_directory' ) vs TEMPLATEPATH

Question

I was reading this article: Common WordPress Development Mistakes and How to Fix Them, and in it, they author says:

Getting the theme location: If you are using TEMPLATEPATH or bloginfo( 'template_directory'). Stop! You should be using the very useful get_template_directory() as seen in my examples above.

But he doesn't elaborate. What's so bad about bloginfo()?