I've gotten used to using ALT very extensively. If you have a scaled battlescape, as I suppose essentially everyone has now, it's not really many screens to scroll to see everything even on, say, 60x60 map (in contrast to OG). Usually I only use the minimap in bug-hunt mode or check how far I am from the borders of the map (also by pressing ALT on minimap to see the borders, if I recall correctly; easily checkable with scrolling as well). Instead of minimap, it's way more convenient to just press ALT to spot the units (also scanned ones), including which way they are facing just to be sure (especially important in mods like XCF where at start you might have tons of enemies looking at some direction and sniper/spotter mechanics make it essential to know which ones have spotted you). This is also true for missions which have multiple levels and you want to quickly go up/down levels with PgUp/PgDown and check which level had the enemy units (that you see with PsiVision for example).
The problems with minimap are that
- it's slow to switch back and forth (multiple times per turn)
- it can be very difficult to spot the units with certainty, especially the blue dots can be really difficult to see if they are standing on top of some item
- the colors on it can be really messy and ugly, I suppose depending on terrain.
- you don't get the precise location so easily if you want to target some unit or its adjacent square (e.g. with a grenade)
It's no big problem for me to get used to pressing two keys instead of just one, given that CTRL and ALT are so close to each other so you can do the pressing with one hand (I have used little finger and thumb myself in my testing) in any case leaving the other, right hand free to do something else, like scroll the map.
I suppose it would have caused least surprise and thus would have been most logical to preserve the existing behaviour with ALT, yet add the new feature using a different keybinding, like CTRL+ALT. But whether it makes sense to change it back this way, or some other way, is maybe another question.