Hi,
I currently have a Fenix 3HR and wear it 24/7-365 and briefly tried a 735XT. I love the functions of the Fenix 3HR but when I tried the 735XT for a week, the size and weight of the 735XT just made med think about selling my Fenix 3HR and buy a 735XT. But the lack of functions, waterproofing and the barometric sensor, put me off. Now the 5S has been announced, I only see two things I am concerned about. Battery life in GPS mode, but then there is Ultra Trac, so maybe not that big of an issue. The other being the short strap on the 5S. It's not even as long as on the 735XT and from time to time I wear it over my clothes. I know there is alternatives, but I do like the silicone straps from Garmin and also non Garmin straps do not have QuickFit, so there goes the clever in QuickFit...
Garmin: A copy of the 735XT band would just be perfect. Same length (or even a bit longer) and with the square holes.