My LGS played with the playtest rules today. my first feelings after playing was that I quite like the hit chart change.
1) it makes shielding damaged parts of the mech possible. I had a heavily damaged right arm and right leg on my Cyclops and by keeping my right side turned away from the banshee it was engaged with.
2) The guy I played against had only been into the game was relatively new and sometimes struggles with the existing side charts
3) It makes fall damage much more interesting because if you fall on the left you will be taking fall damage there for sure.
The ammo explosion changes were more interesting. We had 3 tables playing games and all went about 6/7 turns. We intentionally all built forces with ammo that exploded and most of us brought mechs with no CASE. In those 3 games only 2 ammo explosions happened which I think goes to point out that they really are not actually that common. Ammo explosion 1 was on the table next to me where a T-bolt had the LRM Ammo go up, he confirmed a crit against himself on another ammo bin that killed the mech so effectively the same effect as current rules. 2nd was my opponent who had the banshee lose a full SRM ammo in a stripped arm. He lost the arm 14 points splashed into the torso and he got an engine crit against himself. Not great but still an assault mech capable of doing assault mech things
What I think is interesting is it meant the game wasn't immediately over. By that point on turn 5 I had shot the leg off his Marauder II and it was down behind a hill and effectively out of the game. I had 5 mechs to his 3 even if my Dervish and scorpion were in rough shape. Had he taken the 180 points of full damage from the SRM bin and the Banshee roman candled itself he said he would have conceded then and there but instead we still played another couple rounds and it was uphill but there was actually a game that continued to occur where otherwise we would have just packed up