I think the key distinction that Katz is failing to make is this: switching to Vim is not a matter of 'You’re learning a new EDITOR for God’s sakes. Of COURSE there’s going to be a learning curve.'

As pointed out, Textmate is a new editor and you don't come to a standstill when you use it for the first time. But Vim is a fundamentally different KIND of editor than Textmate. It's not that it's a different program. It's that it's probably the first modal editor you've ever used. As far as I'm concerned, the whole bulk of the first and hardest step in learning Vim is just wrapping your head around editing modally. Whether you want to disable your arrow keys and obsessively leave Insert mode, in order to cultivate good habits, or you just want to muddle through and implement Vimisms where you can is wholly up to the reader. It's analogous to whether you want to cover your keycaps and use dvorak all the time even when you can't touch type, or just ease into it. But the hump, the bit that's a qualitatively different experience, is the modality of the application.