Assessment - doesn't sync but picks up everything within 200 yds
Recount - syncs with other Recount users
Violation - syncs with other Violation users, and picks up data from DamageMeters and SW_Stats
I used to use SW_Stats, but finally got tired of the clunky UI and started looking for alternatives. I've tried all 3 of the Ace-based combat meters I listed above, and have stuck with Assessment. IMO it has the best UI (clicking the bars themselves to navigate is much more intuitive and faster than clicking buttons somewhere else), and after a week or so of running all three, unsynced, alongside SW_Stats, I found that the only place I had a problem with accurate data without syncing was vs Gruul (although the author of Assessment tells me he doesn't have this issue, so that may be a problem on my end), and every other time there was a difference between Assessment and SWS, it was due to SWS missing things.
Recap will do a lot of these things as well, including synchronization (but only with other users of recap).
Here's a link: http://wow.curse.com/downloads/details/5467/. While I'm linking you to curse, this addon is located on the wowace svn (thanks to someone who uploads it every time it's updated) and, of course, uses the ace2 libraries.