Have had the glove radar for 2 seasons and found that it's relatively accurate and excellent to gauge consistency and speed differences in various pitches. I've used it on both fielder's and catcher's gloves.
It's extremely simple to use and so light that you almost don't notice it on the glove. Price is reasonable and it has the advantage of not needing an extra person to run a radar pistol.
Pros: Small, simple, inexpensive, convenient
Cons: Occassional erratic readings
This review was written in the old system and had content requirements that are different than reviews written today.