In case of vim, we need to differentiate between

• first-plateau users (sticking to insert mode, which IMAO vim makes far too easy and comfty) and
• those who overcome this to actually use vim efficiently in normal mode.

These are two vastly different ways to use vi(m), comparable maybe only to the distance between, say, wordpad and emacs.

Still an unconvinced vim user: Do yourself a favour and check out the vim screencast series on youtube, some of the clips are real eye-opening little gems: The secret is touch-typing and muscle memory :).

Update: some related considerations:

• How large is the visual disconnect if padre were to invoke the user's preferred editor for nontrivial edit tasks into a possibly pre-existing editor instance?
• How much is the user hurt in his normal accustomed use, if a new independent editor instance is created?
• How much of a problem is the mismatch/lack of some offerings between IDE and editor, say for tag navigation? Just tiny a bit of extra mousing might lead to a significant workflow interruption...