Geoff Dalgas did a bang-up job implementing the #1 UserVoice requested item -- and he did it all while we were away on our NYC trip, no less!
You'll notice there is a now a Reputation tab on everyone's user page, which includes
a graph of your reputation over time
a summary of the actual up and downvotes from each question/answer that generated your reputation.
The graph is "live" -- you can select a time range with your mouse and drill into the specifics for that time period. If you were ever curious where your rep score came from, now you know. This is also the only place we expose downvote counts.
There is still some tweaking we want to do with the layout, but hopefully this will meet everyone's obsessive desire to track their reputation scores in the minutest of possible detail. Not that there's anything wrong with that. No.
This would not have been my first pick for feature priority development, but it was highly requested, and I thought Geoff did a great job on it.