Yes. No. Depends. If you live out in the boonies, go for it. If you live in the city, no way. Basically, you have to have access to a long, strait, perfectly level road or it won't be accurate. Naturally, low/no traffic. If you want to use the skidpad, same deal. You need a large, smooth, perfectly flat and level area free of obstructions. If you can meet those conditions and you tune it to your car properly, they are amazingly accurate. The only reading I had a problem with using my G-Tech Pro was the HP measurement, because at the time I didn't know the exact weight of my car and had to go off the door tag, and it can't take things like aerodynamics and drag coeficients, wind strength and traction issues into consideration. On the bright side, it will always read less than you have so you know you have "at least x much". It also is enough to know when you change a part if it made a difference. I would say that the HP is the only measurement that isn't pretty much dead on if you use it right. Pretty easy to use, how much use you get out of it is almost completely determined by where you live
I picked up a new g-tech Pro off ebay for $49, the sellers name was gtechpro and I think the price has gone down since I bought it.It works great and I have used it to compare different carbs and for setting up timing,jetting and my accelerator pump.I live about 10 min from a stretch of highway so I go out late at night and do 0-60 runs.the nearest strip is about 2 1/2 hours away so I want to have my car set up before I take it there rather than waste time at the strip doing it.