First off I don't think having "this week", "this month" or "this year" is a good idea; while it's computationally cheaper than the equivalent "last 7 days", "last 30 days", "last 365 days" it becomes kind of useless every Sunday (1st of month (like, uh, today), 1st of year).
This really becomes evident when you see a user's top tags and realize they all come from the same recent question. (Paul Nathan's top tags, e.g., are careers, feature-request and status-planned; hmm, why is that familiar...)
That "problem" (I don't think it's a feature anyway) is also caused because IMHO week reputation and weekly top tags really are kind of meh; it's just not enough data to be representative. The user page would go from "always the same faces" to something quite more transient (and random); I'm not sure I like that.
The situation is even worse on new, low activity Stack Exchanges. Let's look at Bycicles:
Yup! I just signed up. Our favourite unicorn shepherd also gets some first page action with his 1 rep change (or rather, -1 rep change).
Association bonus and downvotes counting in the leagues have been fixed in the meantime, as Jeff points out.
So yes, I'd rather see a last rolling quarter window for something both more dynamic than what we had, more stable than what we're having and more interesting overall.