The lag we are talking about is from the actual GPS chip itself. It only updates its location every so many feet. Which is fine if you moving along at highway speeds, you wont notice it. BUT... take that same mapping application (no matter what it is) and try to use it while walking... you will immediately notice the GPS chip lag.
Theres TONS and TONS of threads regarding the chips inability to handle a high resolution (frequent position updates). Some guy even came up with a work around that extrapolated your position to help eliminate some of the lag.
For those of you whom say there is no lag, do you only use your device when driving? what about walking?
I have started a poll/thread to discuss this so we dont hijack the OP's thread
check it here:
http://forum.ppcgeeks.com/showthread.php?t=99268