I've been lurking this forum for years now and finally have something possibly useful to contribute.  I wanted to post this in the Hashcows thread in response to this: https://bitcointalk.org/index.php?topic=293872.msg3183550#msg3183550

That message was posted right after I started working on a GreaseMonkey script to do almost exactly that, along with some other changes that are mostly personal preference.  This was mainly a learning experience for me, being my first GM script written, but in case others might find this useful before the site actually gets updated with similar features, I can find a place to make it available (and maybe clean up the horrible looking code a bit.)

Anyway, here is what I did so far:
- Difficulty is recalculated as expected number of diff 1 shares.
- Calculates pool rejected % for current round and compares it to user rejected % (green if you are better than pool average, red if worse.)
- Changed estimated earnings to display in uBTC.
- Calculates round profitability as uBTC/hr.

Here is a screenshot of what it looks like.
http://i.imgur.com/POkuwGC.png