I've noticed that my party (including the player character) is hugely underskilled with the current currency implementation and just really weak overall. I feel like currency adds challenge (while also removing the randomness of spirit chime/matrix drops) but it removes a lot of interesting and fun party/skill builds that were once possible with training points. It also means that you'll have a lot of disposable unskilled meatshield demons that aren't integral to your party.
In my current game I'm level 12, with 596 C in the bank on Tower:11. I've lost several disposable demons, but also a cursed asrai used for debuffing and headless, whose diehard ability I couldn't copy to anyone in time because I'm always short on currency. So far I've only been able to afford two demon fusions (which provide 2 skills each by the way! and they are both still alive), 2 PC skill copies, and maybe 8 demon-demon skill copies (of which only 3 skill copies still exist in my party). I've not revived anyone (and probably never will) because the cost is insanely prohibitive. So basically I'm stuck with a bunch of unskilled demons that I don't really have any control over who just melt whenever ranged, modified, or status inducing enemies come into view. And my PC only has TWO copied skills. Another two skills come from heroes; these skills don't really fit the build I envisioned but I have to use them anyway just to survive since currency is in short supply. This *might* be because I might've skipped an optional branch with more currency in it due to running away from a mostly explored floor or two, but I don't think "optional" branches should be necessary to your party's survival.
Overall I'd say the challenge increases but the flexibility of your party and the interesting and fun builds that were once possible are unviable or just impossible now. Sure it cuts down on "village bicycle" skills like diehard, evasion, tireless, etc. being passed around to the whole party, but it also cuts down on the transfer of specialized skills. My playstyle feels severely restricted with the addition of currency.