Hi Nightshade
Elemnt user here....

The screen is easy to read in even the brightest sunshine.
Screens can be modified & personalised so whatever info you need is on display or a touch of a button away.
It operates in conjunction with a phone, not a p.c.
Basic (and I mean basic!) world maps are included with purchase.
Battery life is as advertised, unlike other brands.
Turn by Turn is available (I've used it once, I prefer the chevrons)
I wouldn't know how to use hear rate monitors etc, but these are all available and leds inform you when you're in/out of range.

But....
The one disadvantage for navigation is that once you go off route, because "you" are at the bottom of the screen, it is easy to lose the route behind you. If you go further off route, the chevrons disappear, but the route is still marked in a slightly different shade. Can be a bit difficult to figure out, especially if there are lots of roads in an area. It makes forced detours interesting! :-). I understand that this is a ticket item that will be improved in the future.

I have never used a gps until earlier this year and what swung me to the Wahoo is the usability on the road.
Because it works though an app, once you have your phone you can plan, load and ride routes on the fly.
Currently you need a wifi/data connection to load a route into the app (not the unit - the app), even if the route is already on your phone. Wahoo have assured me that this will be eliminated in an update. When that happens, if you have a maps app on your phone with downloaded maps (eg OSMand), you will have a fully offline ability to plan and then ride a route. The only other unit with this capability that I am aware of is the Garmin Touring - I tried it and it is, as Neil Young sang, a Piece of Crap!

Another thing I'll say is that they customer service is top notch.

If you do a search on these forums you'll quickly find lots of threads discussing the merits of different units. For navigation and hear rate monitoring you're looking at top dollar prices.

Best of luck in your research!

Frank