I can't speak on the limb driver but I just got a guardian and can say to stay away from the limb saver drop away and would recomend the drop zone if the limb driver didn't work out. The drop zone has been great on the guardian. Here is a link to a grouping a shot with the drop zone. I didn't even have 25 arrows through the bow at this point it was that easy to tune.

http://www.huntingnet.com/forum/tm.aspx?m=2184735&mpage=1&key=&#218474 7