Not advanced or useful for the price
I purchased this watch to track my outdoor workouts, whether walking, running or hiking. It looked nice, and seemed to have everything I needed, including a very nice heart rate monitor on a chest strap. Actually, the heart rate monitor strap is one of the nicest designed ones I've seen, including the "standard" Polar version.
Here's what I like about the watch:
1. I think it actually looks cool with the orange strap that is included. Not bad for an exercise watch.
2. It appears to be very waterproof, though I have read several complaints online about it.
3. The GPS seems to be very accurate, and tracks my hikes very well, when compared to my other trail GPS handheld (which has better maps). So, if you get lost, you can follow the right paths back to the starting point.
4. It has a lot of menus and submenus for you to personalize the watch to your outdoor activities.
5. It has a geocaching function, for those into that sort of thing.
What I don't like about it:
1. It's a bulky watch, even if it kind of looks cool. There's a trend in men's watches to make them bigger and bigger, but it's not the diameter that's large, it's the thickness. I actually have to unbutton some of my long sleeved shirts' cuff to thread my arm through. It's that thick.
2. The menus, though very helpful in personalizing the watch, are complicated and sometimes confusing.
3. Battery life is great without the GPS. But forget to turn off the GPS, and the battery is gone in a few hours. Be aware of this problem.
4. My largest issue with the watch is what it doesn't do, but it really should do. For example, it measure distance, heart rate, etc. but it doesn't give you information like calories burned. Or steps taken (if you buy the fairly expensive foot pad that measures your walking or running cadence). Or some other useful workout information. It allows you input your height and weight, but I cannot figure out why it doesn't do some useful calculations.
5. Altimeter appears to use barometric readings. It's got a GPS chip, which gives altitude, so I have no clue why Garmin couldn't have written the software to give a more accurate altimeter reading.
6. The fenix, out of the box, is not Mac OSX friendly. You have to download two pieces of software. One allows you to update the watches' firmware, which I have had to do twice in a month. The other piece of software, Garmin's Base Camp, is OK, but again, gives no really good information about the exercise you've just done.
7. The watch face and bezel are just plain cheaply manufactured. This isn't a $50 watch, it's 8X that. And obviously Garmin is remiss in hiring design engineers for the watch, because it is not only badly manufactured, but badly designed. For example, along the outer edge of the bezel are these indentations that have no function but to accumulate the dirt, oils, and other detritus of a hike.
8. The watch is supposed to link with your iPhone. It does. But just to download data to the iOS version of Base Camp, which gives you even less information about your exercise.
I am very disappointed with this watch, and am considering a return, except it does a few things so well, that I can't think of a way to replace it. The GPS tracking during hiking is good enough to keep me from getting lost, even if there's no map visible.
It really gives you no information about your hike/run/walk that GPS watches half the cost can do. And Garmin software hasn't integrated the cadence + heart rate + distance + time into useful and meaningful information about your exercise routine. Nike and other companies have developed integrated tools, like the Nike Fuel, that connects with computers and iPhones directly to give you up to date info about your fitness and your goals.
If you're looking at this watch for hiking, there are better choices. If you're looking at this watch for exercise, this shouldn't even be considered, it's just plain useless in that area.
It's too buggy
I had this watch for the better part of a year, seeing it go from software v2.60 to v4.00. This was an ambitious project, stuffing a full-fledged GPS into a watch, and so I patiently waited for Garmin to iron out the bugs and make it more stable. And I waited, and waited, and submitted bug report after bug report. By v4.00 I had given up and returned the watch (to REI), since I continued to witness the watch freeze while tracking, and saw it continue to represent my hikes as straight lines on the map page. A little googling turned up forums on Garmin's own forum page lamenting these long-standing problems. What is really striking is that they are rolling this out to military chaps (Garmin tactix) with so money bugs...
If you have the money to spare, yes, it is a cool novelty item. But to replace your Garmin Foretrex 401, or other decent GPS? No, this is not reliable enough to guide you on anything ambitious in the backcountry. You'll wind up the weakest link on your hiking/mountaineering team, head constantly buried in the watch trying to get it to work. Maybe as a training watch, but even then, it's buggy and can take 5-10 (sometimes 30) minutes to get a satellite lock, meaning your friends are waiting for you to be ready. I may try the Suunto Ambit2, its closest competitor, but as of yet I cannot comment.
Some people seem to have lucked out and have great experiences with the watch, possibly pointing to a Quality-Control issue, but I haven't gone through enough Garmin fenix units to know if that's the case.
Alas, a great idea, but poor implementation with regards to the software, even a year and a half after its debut. Maybe wait for the Fenix2 to debut.