Do inexpensive performance meters work!!

If you have considered buying a G-tech or any other performance meter you gotta read this:
http://www.caranddriver.com/features/9380/do-inexpensive-performance-meters-work.html

Thats a great article. All of those units were pretty accurate. The graph makes it look bad but it is in .1sec increments. I have an RR G-tech.