How accurate is G-Tech?

I know you've seen them, I was wondering if anyone had used them and how accurate they were? Consistent?

From what I hear, they are very accurate. They claim that they are within 1/10th of a second accurate. I seen a review on one and the guy said that with a few runs average it was almost perfect. Consistency should be the same. Horsepower is like within 1 or 2. I've heard that with the way that it measures the HP, that if you remove your mirrors and ducktape your headlights, it will read better HP. I would trust it though.

i've heard very good to very bad things. from being 100% dead on to up to 7/10 on 1/4 getting 20hp less to being right on. I think its not a worth while thing to get youd get the same #s with armchair modding