Sky-High Ambition v4 adds some very cool new things. A map with event spaces is awesome, leveling up your yakus and unlocking new special yakus adds another form of scaling I like, and while I haven't tried the other characters that sounds like a nice extra to add more variety.
I want to like all of this, but the core problem I have with the mode remains. It is trivially easy to win a run - see this score I put up on day 1 with no unlocks - and so there is nothing further to do but grind big number in Endless. And Endless fucking sucks because getting a leaderboard-worthy score is all RNG, in fact it feels worse now because you don't get to engage in those cool shiny new map events during Endless.
I had more fun with Balatro when I stopped playing Endless and just let all my runs end at Ante 8. If Sky-High Ambition had a Gold Stake or Ascension 10 or whatever where getting to the end screen was challenging enough for me to be satisfied stopping there, it could be fantastic! They're so, so, so close to having a much better game on their hands, this is all they need to do.