Phase 1 of the melee changes have now been in the game close to a month and I feel that's enough time to give feedback on it. This is my personal experience and feedback.
I'll try to list what I feel is good and bad about it, with my thoughts on how to improve it as sub bullet points, if I have any such thoughts.
The Good (With and without "Melee with Fire Weapon Input")
Directional ground slam is a great step in the right direction. But it doesn't feel finished.
The speed seem to have little or no acceleration which feels off.
The animation at the end of the slam is too slow. Many times you're better off just falling and landing like normal.
Does it have to be all or nothing? Some abilities will stop the animation completely (which I think is a bug or oversight) What if we could do a second jump to break the animation and then slam again? I think that would enhance directional slam overall.
The Bad (Both modes)
The auto-block when you have your melee weapon out (now? don't remember it slowing you down before) slows you done while jumping. This feels really bad. Suddenly the range of your jump will decreased and I won't end up where I expected to. This especially harmful when jumping over areas where if you fall down you'll be despawned.
The Bad (Without "Melee with Fire Weapon Input")
Smashing E to use melee feels weird and clunky and since the stance applied I kept doing weird moves I did not wish for. With this enabled I found myself constantly doing spin attacks instead, since that what was what felt the least bad.
I switched to "Melee with Fire Weapon input" to get back the ability to use melee with my mouse button again.
The Bad (With "Melee with Fire Weapon Input")
I constantly find myself using the wrong weapon type since I just did an aim glide, so the game switched weapons for me.
I've tried to aim glide less, but it's such an integral part of the movement, that it severely slowed me down. And even after close to a month of trying to change and get used to it I simply haven't been able to.
The directional ground slam is a step in the right direction in my opinion. I think it just needs a few tweaks to feel great!
The quick switch melee on the other hand is not, and it's hurting the fluidity of the movement and melee system. We've also lost the ability to quickly use our melee weapons without having the drawbacks of melee combos. Many of said combos will catapult you several meters forwards, often into a despawn spot which severely punishes you. Overall my enjoyment with the game has decreased since these changes where implemented.
I wish DE would remove fast weapon switching completely, and give us back quick melee attacks. Then just decrease weapon switching times across the board. This would prevent confusion from having the wrong weapon after doing an aim glide and the bad feeling from having to smash E to melee while still retaining a fluent melee combat system.