Every time I try an IDE (admittedly not very often) I end up frustrated that its Vim binding implementation is incomplete. It feels even worse than using its default bindings because I start to feel confident and then suddenly it doesn't work as expected and I feel cheated :-) I guess after a while you learn what to expect from the Vim implementation of your IDE of choice but I haven't yet had the patience to reach that stage.
I think XCode's new vim mode is the only time I've found it truly jarring how incomplete the mode was, but it's certainly better that it's there than not.
