Lets hear some reviews, comments about the maps feature

Just go to GPSFileDepot if you're looking for Topo stuff in the US. Pick what you're looking for, download and install it on your PC and then run Garmin's MapInstall (get that from their site; it's downloadable.)

It will "see" the maps you installed and give you the option to manage what's on the watch.

OpenStreetMap looks like it's a road database. You already got that on the watch in the US at least..... and it looks pretty complete and up to date from what I can tell, so I'm not sure why you'd want to replace or augment what's there in that regard.

For the topo side it's primarily a matter of wanting 1:24 instead of 1:100. The latter is on the watch already; the former is a lot more-detailed and has nice elevation contours, etc -- but, is generally not routeable unless you buy Garmin's. There is an alleged OSM Topo Routable set but I don't know a lot about it and haven't looked into in detail but if I recall while it has elevation contour lines they're missing numerics (!)

transfer maps from gpsmap 64 to Fenix 5x

Is it possible to transfer my img map files from my garmin gpsmap 64 to a Fenix 5? Ive got the UK OS 1:25000 mapping on the 64 and wondered if I could get them to work on the F5X.

The F5X still isnt freely available here so I cant just test it out at the moment unfortunately

If Maploader will recognize them then it's trivial. Just have it load them, yes it will work.

If not then you can try dumping them in the Garmin directory and see what happens, or dump them in CustomMaps under Garmin. Either MAY work. But if you loaded them on your other Garmin GPS with Maploader, then it should definitely work to load them on the 5x -- that's how I got my 24k Topos on.

The map probably has unlock key for gpsmap 64. :p

If they're Garmin's purchased maps, then yes, they may well be locked to the original unit...... If they're one of the "open" map databases that are around then they should work.

OpenStreetMap looks like it's a road database. You already got that on the watch in the US at least..... and it looks pretty complete and up to date from what I can tell, so I'm not sure why you'd want to replace or augment what's there in that regard.

For the topo side it's primarily a matter of wanting 1:24 instead of 1:100. The latter is on the watch already; the former is a lot more-detailed and has nice elevation contours, etc -- but, is generally not routeable unless you buy Garmin's. There is an alleged OSM Topo Routable set but I don't know a lot about it and haven't looked into in detail but if I recall while it has elevation contour lines they're missing numerics (!)

Plenty of OSM-derrived maps are routable and for something other than driving on roads: see OpenCycleMaps, OpenMTBMaps, etc.

I like the idea of using non-garmin maps as some are free and some (like a paid map I have) include quite a bit more info than the Garmin 24k topos. However, none of the ones I've tried work with the elevation plot on the watch. Am I right that for this to work the map loaded in your activity must have built-in DEM data? it seems Garmin's topos do have that, but I can't find any OSM or other good topo sources that do.

Also, will tracks I create in programs where the underlying map does not have built in dem data have working elevation plots on the 5x if the underlying map on the watch has the dem data?

I like the idea of using non-garmin maps as some are free and some (like a paid map I have) include quite a bit more info than the Garmin 24k topos. However, none of the ones I've tried work with the elevation plot on the watch. Am I right that for this to work the map loaded in your activity must have built-in DEM data? it seems Garmin's topos do have that, but I can't find any OSM or other good topo sources that do.

Also, will tracks I create in programs where the underlying map does not have built in dem data have working elevation plots on the 5x if the underlying map on the watch has the dem data?

People have created OSM-based maps with integrated elevation data. Look for topo maps with integrated contour lines. I have found some here and there that are free, while OpenMTBmap seems to have worldwide coverage but requires a ~30 euro subscription to get the countours and integrate them.

From what I have read, there are two ways Garmin maps can show elevation profiles on a route: either if the map has Garmin's proprietary DEM (e.g. shading relief) that somehow shows an elevation value for every single point on the map, or if the map has contour lines (in which case the elevation is calculated based on where the route crosses contours).

I don't have my 5X yet, but I have been playing with this in BaseCamp. I downloaded free OSM-based maps of Chile from a variety of sources (hiking in Patagonia next month). The free OpenMTBmap version had the best and most complete trail layout for the place I'm going. I used that to create a hiking route from point to point, and it automatically routed along the correct trails. Then I switched to view the same route on a map with integrated contours, and it shows an elevation profile (though maybe not as smooth as if I had a Garmin paid topo map).

For the money, I think I'm probably just going to pay for a 1-year OpenMTBmap subscription, download everything I could ever imagine using, and integrate contours. This isn't exactly free, but it isn't anywhere close to what Garmin would charge either. And I don't need an elevation profile that shows every little up and down < 5m ...just the broader idea would be fine.

If they're Garmin's purchased maps, then yes, they may well be locked to the original unit...... If they're one of the "open" map databases that are around then they should work.

That's great, they are unlocked OS maps, Ill give them a go when the 5X comes available