with geotagging you should be aware of the limitations of this devices. It can happen that some of these devices do not work properly in forests, gaps, or towns with narrow roads and high buildings. And indoors is certainly also not possible, as these signals are very weak. Try to buy a unit which has the new and better SiRF Star III receiver, which is much more accurate and for example works also inside the camera bag, as long as you put it not under three layers of cloth or camera gear. It might be not important outdoors, but walking around in a big city, going with the underground, I certainly do not recomend to use expensive units like that attached outside of your camera bag.
Garmin devices have the bonus of working as a true gps, which can be a plus for hiking as the track back function is a kind of safety net for situations when you have lost orientation (snowstorm, fog,...) but you have to remeber to put it on all the time and only the active log is showing the time ! A saved log at garmin devices does not have time information and is useless for geotagging ! So not very practical for long trips, as you need a computer to download the active log.
