In the world of golf, there are two major categories when it comes to rangefinders: laser and GPS. Both types of units can be really good but neither is without fault ether. For instance, lasers are deadly accurate and can be used on any course, but if one suffers from shaky hands they can be a pain to use.
In addition, you have to have a clear line of sight to the target to get a reading. GPS range finders, on the other hand, don't need that line of sight and all you have to do is look down at the unit for your yardage. Unfortunately, GPS presents new problems. Sometimes, a particular course is not available, you might not be able to get yardages to locations other than the center of the green, and the overall accuracy is diminished compared to a laser.
With the release of the upro mx+, Callaway is looking to alleviate many of the issues with GPS units.