I have one from Harbor Freight and is accurate but is difficult to use because it sits high. A few months ago I finally opted for one of these and I am extremely happy with it. Considerably more expensive than the $12 one from Harbor Freight but easier to use and extremely accurate.
I've found this link interesting: http://www.polkaudio.com/forums/showthread.php?t=67124

I tried my digital scale at slightly different heights and the difference was extremely small...like 0.01g.
PM sent.
