My Forerunner 305 has been pretty accurate for me. I've looked at the last several rides using the "View In Google Earth" option, and the overlays have been lining up extremely well with the roads and trails.

I used it to log my route during some orienteering events, and noticed a few small skips or inaccuracies, but that was stuffed in the bottom of my hydration pack in a thick forest, and all the offs were shorter than my actual path, not longer.