This new Garmin 1040 was an upgrade from my old 820, these aging eyes appreciate the MUCH larger screen / display. Also very much like the fact that the display is "ON" all of the time (I've already sold the 820, there may have been an option to have the screen on all of the time on that old unit, and I just didn't know of it). Regardless, battery life on the new 1040 seems excellent. LOVE the many options for data field display, easily configurable. Also, completely seamless and easy transfer of settings and preferences from old unit to new, that was welcomed. Garmin does it right!
It seems Garmin is finally getting better at managing devices as a whole. Settings from previous unit are applied like getting a new phone. The management of maps is much easier, but storage is still too limited. I do like the climb pro for all hills not just when you are on a route. I do not know if I would have bought one just for the sake of it, I liked my 830. But it was a few years old and the new units battery lasts so much longer. I never had issues with the touch screen only on the 830 but it is nice that this one has both touch screen and buttons.
The K-Edge Garmin Max XL Combo Mount (31.8mm) is probably the best option out there for an after-market Garmin mount for larger Garmins (1030/1040), with camera or light mounting. Built quality is high as with all K-Edge products, and integrates cleanly for mounting in-line with bars. I prefer this as it is sleeker and cleaner visual cockpit. I also love using the standard GoPro mounting for my occasional action camera use, or more frequently a light for commuting. This option is the correct choice for the (industry) standard 31.8mm handlebar width.
I purchased this as on upgrade to the older 520 model. The 840 works really well and provides a lot of useful data while riding and post ride. Works well with my AXS Power Meter and nice to track both heart rate and power real time while riding. Only negative, this could be I have something set wrong, is that when connected to my Garmin headlight it would run the headlight on full power and drain the headlight battery in two hours. Not a huge issue for me. I disconnected the headlight and now it stays on daylight flash mode and last up to eight hours. Nice upgrade, solid GPS and works well with connected devices except maybe the headlight.