Yea, I did have a look at it, it's very nice.
The way I've implemented it so far is a bit different; instead of going strictly by months, it allows the admin(s) to define any sort of period as a separate group or event, and then contains its own high scores for that. So it's more work, in that the admin would have to manually start a new group for each month, but it can also be reset more often if necessary.
I'm still testing it, and it won't be in Beta 2.1, but it will still make a showing in the vB2 version of the hack.
Your site did inspire me to start thinking about an optional cron job that could automatically rotate the scores each month/week/whatever.