GPS with m4/3 - Best Combo of Unit and Software?

Since no m4/3 camera currently has the capability to add a GPS unit that writes GPS data to the image file at the moment of exposure (as some Nikon and Canon DSLRs do), you have to use an external GPS unit and software to sync the data at a later time.

Is there any GPS unit/software combo that works better than others? Or is it pretty much equal between the various choices, and just comes down to how well you can match the times in the GPS data with the times in the image files?

Thanks. I keep hoping that either Panasonic or Olympus will see the light and add GPS capability (at least via an add-on unit) to an updated G5 or OM-D or equivalent ... .