My main is an arms warrior (33/28/0 --> PvE, blood Frenzy). One of my main damage skill is slam. However in order to provide a decent DPS, timing is VERY important. I must hit slam as soon as my auto-attack hits. The use of a swing timer helps a lot and for that I use LD50_abar.
There is one thing it cannot do at the moment : it doesn't provide any measurement of your timing. What I mean is that if you use slam too soon, there is no way to know by how much you hit it too soon. The same applies if you hit it too late. What I would like to see is an add-on (or maybe a LD50_abar hack) that would allow to display your slam timing from your last auto-swing.
In that last example above I hit slam at 0.1 seconds before my next auto-attack, (which isn't good, as slam resets the swing timer) I displayed (-0.1) as it made it easier to see it was too soon. (I would do that only past 80 % of the swing timer's timing)
One thing I would suggest though is to look at the changelog and if the latest additions don't interest you
pick a previous version from Archived
(I'm staying with r12, it's bug-free and feature-complete for my needs I don't need the extra stuff added after it)
I dunno why, but it stopped right after I disabled it.
Looking at the comments over the download site (Wowinterface) I don't seem like the only one having that issue.
Ok I take it back.. I should have said "the version I'm using is problem-free".
The problem comes from r13 (and later probably) attempt of the addon to take an automatic screenshot on boss death.
If you don't need that feature I'd suggest staying with r12 per my initial suggestion.
It's been a stable version in my experience, it has the slam timer feature you were looking for and no extra "fluff".
I've been raiding with it before and after 2.4.3 and never had problems with the social pane.