The vi tag is unavailable - it's considered "intrinsic" to the site; every question is assumed to be about vi or a derived editor unless otherwise noted.
...Which means it's important to tag questions that aren't about vi with a tag that indicates the specific editor being asked about. Chances are, vim will be the most common tag here - [Update: that's not working either; folks don't use it consistently at all. It's now blacklisted too.] What's not ok is failing to use other tags to indicate the specific nature of the question. You'll need tags to indicate...
- ...the OS platform being used
- ...the specific editing feature being asked about
- ...any relevant add-ons being used
Comprehensive tagging is important to establish early - that's why during this private beta, anyone using the site can create new tags. But do exercise care: more tags are not always better. Strive to create and use tags that are both descriptive of the specific topics being asked about and generally useful to others interested in the same topics.