Just got the Fenix 5 Sapphire bundle today.
I also have a Polar V800 which I have used for 3+ years and really like. Running, lifting, cross training, yoga, etc. I'm not a biker or a swimmer though.
First impression, the Fenix 5 is a beautiful watch. The weight is indistinguishable from the V800. Band is thinner than the V800 while the face is larger and thicker, but not to the point of feeling overly large.
Minor disappointments:
1. Low contrast display. I have trouble seeing the time in low light conditions where is is not problem with the V800. Maybe the sapphire glass?
2. Extra band was not included in my kit. I will talk to REI about this tomorrow.
3. First workout I paired the V800 to a VIIIIVA HRM on the bluetooth side, then paired to Fenix 5 I assume using Ant+. I lost the HRM a couple of short stretches on the Fenix 5. Also the calorie burn was about 20 calories lower on the Fenix but I have no idea which is correct in that regard.
Overall great watch. Still playing with settings etc.
Looking forward to a run tomorrow to compare the GPS tracks, which has always been good on the V800.