See
http://www.lucasforums.com/showthread.php?t=163752) for a discussion (ad nauseum). But you already knew that.
The short answer is: Zoom in and aim about the middle of their body (down halfway, in other words) and it works like a champ. I spent about 2 hours on the training map. After being the sniper, I sat up on the perch and waxed droids until I got the award rifle. I then spent the rest of the time getting familiar with it and where to aim. I could hit extreme range targets no problem by the end of the session. I had like 200 kills--great fun!
Even funnier, on the Training Map, I figured out the effective range of my grenade throws and was able to hit the spider walkers and TOOK ONE OUT with about 6 grenades! All from on top of the high command post. The bad thing is if you miss the sphere part of the body, it lands in the midst of a running gunbattle and you will probably get friendly kills.
Hope that helps.
* SithSpeeder *