Playing through SMT4, about 20 hours in. I finished Nocturne in early September and waited a bit before jumping into this. I have to say the game's balancing feels totally awkward in comparison.
I think this is attributed to a lot of things, but one thing I've really noticed is that it feels like everyone does more damage and has less health in general, including yourself and bosses. This kind of exacerbates the one-sided fight problem I think press-turn games struggle with. In Nocturne enemies characters were hardy enough that even suffering a big disadvantage you felt like there was a chance to come back from it. There was tension. But here everyone is so squishy that fights tend to last 1-3 turns max, and if a boss goes on the first turn and gets a lucky crit or something there's a very real possibility you can get killed without getting a chance to do anything. Props to the game for a particularly annoying recent battle which was going fine until one of my AI companions hit an enemy with an element they absorbed, giving them smirk for the next turn and nearly wiping me out in the process.
Speaking of smirk I'd heard all the complaints about this mechanic, and it is a pretty bad one. I think I can see at least some of the reasons it was implemented, like discouraging you from hitting groups of enemies with random aoe spells because you know the consequences won't be that big even if one of them nulls it. But it just makes a battle system that already feels very luck based lean even more in that direction. The gameplay really hasn't drawn me in all that much, the boss fights don't feel nearly as strategic or unique as many of the ones in Nocturne or DDS did, where so many of them felt like they had their own gimmick or unique mechanic attached.
On the other hand I really like the setting, the post-apocalyptic Tokyo feels incredibly well realized, though also probably a bit too ambitious for the game. Looking at some of the (amazing) concept art it's obvious they couldn't fully capture their vision with the 3DS hardware or their limited budget. I've heard Apocalypse addresses a lot of the gameplay complaints people had with SMT4, though suffers in other areas. Looking forward to getting to start that afterward and see how it fares.