anyone have any experience with the g tech pro ss? i'm thinking about getting one just to play around with. are they as acurate as advertised?

They can be fairly accurate if the road is completely flat (like within a couple of tenths). If you start to go up a hill, the accelerometers will read this as extra acceleration and decrease your times (and vice versa for downhill). My brother g-tech'd his 94 Ford Taurus up something like a 5% grade onramp to a highway and got 0-60 in 4.6 seconds.