I on the contrary really like the changes.
In 3E, every demon seems to have some kind devil equivalent and vice versa. The only difference between demons and devils seems to be that demons are labeled chaotic, and devils are labeled lawful. But what's the real difference between them? They are both after souls of mortals, and they hate each other. Their alignment difference don't seem to matter in the actual structure - their are Arch Fiends and Demon Princes ruling over the lesser devils/demons.
In 4E, the difference between Devils and Demos seems very obvious.
Devils tempt mortals to get their souls. They use trickery over brute force and manipulate other beings. Sounds like something a lawful evil creature should do, because it's about long-termin planning and fine-tuning your devil contracts so that they do what you want.
Demons want to destroy the world. No need for plans or structure, as long as you get to kill someone or destroy something. In fact, any kind of plan or structure revealed to a demon is a target.
Demons automatiaclly become mortal enemies of devils. Devils want souls, and a destroyed world doesn't give it to them. Devils devise complex plans to get their goal, but a Demon loves to wreck with these things.