Purchased this watch as a replacement for a Suunto X9. Overall, the X9i is a great improvement over its predecessor. The USB interface and charging system are much better than the old cradle. Battery life is also significantly improved. One disappointment is the removal of the ability to calibrate the altimeter by setting the reference barometric pressure. With the X9i, the only calibration option is to set a known elevation into the watch. As for the GPS functions, there are performance improvements over the old watch, but it is still slow to acquire an initial position and loses satellite lock quite easily due to the antenna design. Like all GPS units, tree cover or anything that blocks the unit's view of the sky will degrade signal reception, resulting in inaccurate positions or loss of signal altogether. The X9i must download satellite almanac data every time the GPS is turned on, and so it can take a really long time for it to acquire an initial position. Unfortunately, there is no provision to manually enter a known position, which shortens the acquisition time in other units. The included Suunto Trek Manager software is quite good and is essential for building a route to transfer to the watch. Overall, it's a good, functional watch, but because of the inherent limitations of putting a GPS into such a small package, you're better off using a traditional GPS unit with mapping capabilities (such as the Garmin GPSMAP 60CSx) for serious outdoor activities. I mostly use this watch for the altimeter and compass features, which are excellent. The GPS feature is best used as a back-up source of position information.