I agree with @gilles that for MVP we shouldn’t display a single reputation number, because once we give it we’ll never, ever be able to take it away again and, demonstrably, we’re not clear yet on what we really want.
Not MVP: I find myself thinking in terms of a set of “stats” on the user profile page, something like:
Questions: 147 posted, 592 total votes, newest (date), top tags: (list)
Answers: 365 posted, 2161 total votes, newest (date), top tags: (list)
Edits: 79, newest (date) [these will be edits to other people’s posts, not yours)
…
This sort of thing gives people a sense of the user’s activity, and also feeds into the idea of privileges based on related activity rather than a total score. It could also feed into something like situational flair later – when a user with X total score in a tag answers a question in that tag, add some sort of doohickey below the user name to convey “subject-matter expert” in that context. Not saying we should necessarily do it, but this approach could enable it if we want.
With the profile also linking to all of a user’s activity, anybody who wants to take a deeper dive can do so – but we recognize the multi-faceted nature of a user from the start and don’t try to summarize it in one number.
If, later, we decide we want one number, it’s easy enough to add at that time.