What makes you think I underestimate them?:) Sometimes they just don't have enough strength to charm an enemy unit:) And then they're not very useful.... If you're fighting neutrals, I agree (it's fun when two enemy units fight each other:D)
I also get new dogs towards the end of the game.... but sometimes it's a bummer that you can only hit six units with the first move:(
As for the horses.... you can get new ones for variety.... but I feel bad sending them into the thick of the battle:D, and honestly, there's not much difference between them..
And still, I think the new alternate upgrade is inferior to others (other races, not just the standard demon upgrade).