Hi! I saw several friends playing this game on twitter and I've been sinking many hours into it since I bought it this Friday, good stuff.
Here's my in depth experience/observations followed by some features I'd like to see
My Overall Experience
For background, after several playthroughs where I would go bankrupt, I felt kinda railroaded into focusing on hardcore fans only just to make money, so that colored my experience. I didn't bother training my idols/enhancing their stats at all.
It was frustrating at first to understand what needed to be done without a tutorial (But I'm sure there'll be one in the final release/explanations of each management tab when first playing) so I had to restart a few times before I had a good enough understanding of the game to not fall into overwhelming debt before having any means to produce singles/shows etc. By the fourth/fifth playthrough I was finally able to turn a profit after organizing the second concert, although I was having a glitch where idol's initial satisfaction with their salaries didn't change so I didn't have to deal with that until I updated to 9.1, so that might've kept me in debt for longer.
I liked how challenging it was to have slightly manageable debt: Contracts were helpful but not super reliable at the lower star levels so I was having to plan out how to finance concerts, singles, and shows that could help increase cash inflow despite having to take loses while taking out loans to actually release things. It made me pace myself and it felt very rewarding to see the expenses eventually be outweighed by our revenue! Finally being able to host a senbatsu and seeing the results was also fun.
My Observations
(As a disclaimer, my salary satisfactions were not changing until the update so that could've obviously made my game easier.)
I feel like the pacing/balancing of the game is off: the beginning once you get the controls down is pretty slow with only incremental developments as you struggle to get to ~6 singles for your first concert, all my runs begin that way with just working to a concert with singles that aren't really markedly more popular than the last one or very helpful to the finances situation, they're just a means to the end of getting to concerts, which are profitable.
The "mid-game" is the part I had the most fun with, where you can afford to take on more idols, start upgrading the copies of your singles/venues for your events and have a bit of freedom to decide how you'll both get out of debt and how you will continue making money on top of that
The "late-game" by contrast was my least favorite part to play, where your fame is rising very quickly and the singles start printing money because of how powerful having a large hardcore fanbase is (And then add in handshakes!). Even by the time the update restored salary dissatisfaction and I adjusted them to bring everyone to a reasonable level, those expenses (~1.5M) were a drop in the bucket compared to my coffers at that point (600M). Concerts grossed 80M, singles also did 80M: I had gotten to a higher fame level with several popular stars but it resulted in a snowball effect that wiped any difficulty via being restricted by money. I could take several more expenses without worrying about it. I was turning down Deals Lvl 10- contracts without even thinking about it as they weren't ever going to be more profitable than a one-off single. And this is with about 150k fans in around two days of play on that game.
So if I had to chart pacing: it'd be like:
Early (No stars-2): very slow
Singles don't have impact, probably need alternating loans from Fujimoto and the bank to not stay in debt over a month. Fujimoto's loans having conditions after taking them was a nice touch that added difficulty/an element of planning and timing.
Mid (2-6): good
First concert, starting to become independent from loans, singles show noticeable growth and change depending on your choices, exhaustion/injury and idol selection/recruitment start mattering
Late (7-10): over-accelerated
Releasing a single/concert just prints money and makes any expenses you have 0
While difficulty is;
Early: high w/o tutorial, autopilot w/ mechanics mastered
It feels like a lot of the game doesn't properly start until the first concert happens
Mid: challenging
Late: low
Seems like there's nothing left to conquer after your fourth concert or so, I hadn't even had enough time for girls to graduate at this point
This is getting kinda long so I'll make another post detailing some features I think would be cool to see!