I would like to preface my post by clarifying that I understand that the purpose of Brawl+ isn't to make Brawl more like Melee; however, I feel some comparisons with Melee are appropriate since, despite the character imbalances that stemmed from chaingrabs and wavedashing, there are many aspects of the game that Melee got right. Anyway, it's been less than a week since I started playing Brawl+, but I have two concerns to offer:
1) Although the default Powershield/Perfect Shield window in vBrawl is reported to be 4, and the window is supposedly only 2 frames in Brawl+, I'm only getting 3 frame and 1 frame windows respectively using the Debug Pause code. However, even if this were corrected, I fear 2 frames may be too short a window. Melee's Powershield window was 4 for melee attacks and 2 for reflecting projectiles, and I remember that reflecting projectiles was really hard to do at will. Considering that Powershielding is difficult to take advantage of since it requires prediction and certainty about the opponent's attack, and the window to react upon accidental Powershields is very small, perhaps returning to vBrawl's default window should be considered?
2) Hit Lag. As far as I've been able to tell, the new landing lag and shield stun values mirror Melee's reasonably closely (with L-cancel taken into account, of course), I notice that Brawl+'s Hit Lag values seem to be consistently and considerably lower than Melee's. For instance, Ganon's mighty F-air had a considerable 7 frames of Hit Lag, and now it's been reduced to 4. Likewise, his d-air had 14/9 frames in Melee (hit/shielded respectively, because of electric attack's lag multiplier) while it's only 5/5 frames in B+. More markedly, Samus's Charge Shot used to be 15/10 in Melee, now it's 6/6.
I understand that this project is a massive undertaking and that's why feedback is valuable to you guys; so I'm basically wondering if you kinda winged it on the current Hit Lag multiplier in Brawl+ or if you deliberately meant to reduce hit lag to sub-Melee standards. I fear that the hit lag reduction is just a bit severe. I've been out of the Smashboards scene for around 2 years so I don't know if this ever got out, but bear in mind one thing: Hit Lag doesn't just dictate your window to Smash DI when you get hit. It's also possible to Smash DI while shielding in order to either decrease or increase your distance to the opponent. This technique could be employed in Melee to, for example, stay within shieldgrab/up-smash range after blocking attacks like Ganon's f-air or Samus's d-smash, avoiding sliding off the edge when standing near it, or increasing your distance from Fox during his d-air to try to cause his shine to miss and punish him.
This shielding Smash DI is still present in Brawl (very easy to tell if Debug isn't available by shielding Halberd's Combo Cannon laser and smashing left or right repeatedly,) although the insane buffering window made it impractical in vBrawl since even if you succeeded, the low hit stun meant you'd almost invariably buffer a roll as well. Brawl+ doesn't have this problem, and the technique may prove even more valuable here than in Melee since Brawl seems to have lower traction overall; but I fear that just like vBrawl's window of opportunity was just too big (consistently 2-3 frames bigger than Melee), Brawl+'s may be too small. Smash DI'ing a shielded attack and punishing was already hard to do in Melee against everything but the laggiest attacks (e.g. Ganon's f-air, 7 frames), and even then it required foresight and carried with it the risk of starting a last-minute roll and getting hit during the start-up if you timed it too early (or becoming too fixated in anticipating the attack and getting caught by surprise.) I think, with the hit lag as it is now, it'd be downright impractical to employ such techniques in Brawl+.
EDIT: Oh yeah, too low hit lag also adversely affects your ability to Smash DI against the side of the stage to tech it when being edgeguarded.