How do most feel about the GPS options on their Dashcams? Do you really feel it's a must have option? If you could save $10-20 on a Dashcam by not getting the GPS feature, would you?
Ask yourself what kind of events do you foresee happening - events that you would take the time to remove the card and copy to a PC? Would any of those 'events' benefit from (or be harmed by) having speed/location data available?
Personally I see far more upside to telemetry:
1) Mapping of your drive will help you quickly find a specific location/incident/area of interest
2) Determining distance traveled between any two points during playback
3) Stopped for speeding? Verify what your speed was to see how accurate the accusation is...
4) Having your documented speed after an accident may help to prove speed was(n't) a contributing factor
5) Ability to document the speed of another vehicle, to report the driver for driving excessively fast (or slow)
6) Verify how fast the mechanic/valet took your car during his "test drive"
7) many more I can't think of (too tired)...
The only downside, other than cost, is the possibility that your speed data could be used against you in the event of an at-fault speed-related accident. But remember - while having the data imprinted on the video certainly makes the cop's job easier, even if you don't have GPS, if they're motivated enough, they can use objects in the video and some simple algebra to determine your speed anyway.
Just this week, a friend suffered severe damage to the tow vehicle behind his motorcoach. He was on a road with a 40mph speed limit, and hit a somewhat innocuous dip in the road. The jarring caused 4 of the 6 bolts in his tow plate to sheer off, which in turn caused extensive damage to the tow vehicle. When he told the dealership (that installed the tow plate on the car) about the sheered bolts, they accused him of hitting the dip too fast. Fortunately, he had his dash cam running in the coach, showing that the dip was relatively mild, and his speed was only 27mph. Who knows how that will turn out, but having that speed documented is certainly not a detriment.