I am using a DIY WB, (well, I got the board, parts, started to assemble it, and ran out of spare time) so I have the techedge, which is very nice, and priced decent, especially since it includes the display, which I can't make anyways. Anywho, it is very accurate, as far as my comparisons go. I need to start datalogging to get a hardcopy, but in just watching the display, it is pretty close. The one thing I have noticed is that it is almost the same as the tailpipe WB on the dyno. I have 2 o2 sensors, one is new, the other is from a civic vx, with 100K miles, and they read within .2 of each other. I wonder if the tailpipe dyno can account for how far back it is, and give a better reading, as I have the WB I use in the o2 bung.