With WAAS you can acieve accuracy within a couple meters. I find my Vista to be incredibly accurate. However, I believe the problem is not the technology but the level of detail provided by Mapsource. The detail is certainly lacking to a significant extent. Just for starters, entire lakes are often excluded, contour lines are often innacurate and terrain is misrepresented. Still, what is available right now is amazing and saves an incredible amount of time that I used to spend staring at maps.