The GPS performance and satellite reception seems very good and it locks up faster and with less signal than my GPSMap 60CSx.
The display is clear, though not all of it is active (main active area is 21mm octagon) and like all modern digital watches the display is recessed quite a long way below the front glass/bezel. The backlight is very good.
The builtin compass seems very stable and accurate.
The Fenix has a USB 'clip' that used for both data transfer and charging. Its sad that Garmin keeps creating custom connectors and this one comes with a built in 1m cable. As if I don't have enough cables, adapters and metres of USB cable to carry around. What is good is the watch appears as a simple USB storage device and the recorded data is stored as GPX files.
The Fenix 'bundle' includes a HRM. The HRM with the Fenix has the benefit of a detachable, washable strap. It also packs up a bit smaller which is helpful. Other than that it just works.
Fenix has a builtin temperature sensor, but its hard to get much useful data from that since it picks up body temperature. However, there is also an option of the Tempe external sensor. The Tempe is a great solution and gives a genuine ambient temperature. Tempe is a lot smaller than I had expected (about 34x24x7.5mm) and the biggest problem with it is that there is no way to attach a line to it. Tempe come with a clip that can attach it to a backpack strap, but I do wonder how long it will be before it gets hooked on something and sprung from the clip.
Tempe doesn't respond particularly fast to temperature change, so a wrap of electrical tape won't hurt. All that said, if you are interested in logging temperature on your hikes, its really useful.
There is also a cadence sensor option, but I've not tried that.
All the sensor data gets logged in the GPX file.
Mechanically the Fenix seems robust.
Battery life; With a track points dropped every 4 seconds, an eigt and a half hour trip left the battery about 52%. Saving that track took over 4 minutes to save. Connecting to a PC with the USB clip takes arounf 40 seconds for the drive to appear. Charging from 52% took about 1 hr 15mins. Thats about 1% per minute and a half.
Overall the Fenix is a great unit, but there are a couple of things that are slightly sloppy and let it down.