So, this may be long, I had my first proper gig with ST4, my impressions are mixed
some is personal opinions, some may be more general.

Let me start by saying that I sing praise to Peter. He is a genius. He made ST3 so good, and
the concept for ST4 is fantastic, it can be the best thing ever, but there are many buts for me.

I will try remember everything, I may not go is order, and positive and negative may pop up randomly.

While ST4 is packed with more, and better features, in many ways it is more complicated, and more complex and harder to navigate and slower to get simple tasks done, LIVE, not sitting in front of the ipad calmly, LIVE.
Some of the menus, some options, man, I couldnt even get to or remember how to get done. like clear "done" tags.
Cmon.....it should'nt be this hard to find.

ok
the mixer is great to look at, but to operate live?? oh no.

Please i am begging!!!! removes the dbl tap and remove the touch anywhere by the faders to move the faders!!!
every mixer i ever worked on, and i have worked on almost every one of the digital ones, only touch the actual "kbob" and find a way to make it glow and maybe even grow, but for cry out loud, no no no!!!
in a gig while im trying to play guitar and look for lyrics, the audience, where I need to click the next button on the Helix with my foot, OMG how many times tonight did I either move a fader to some place louder or softer or it just decided to DBL tap and reset.
THIS CAN NOT BE THE WAY FORWARD!!!
allow us to scroll left and right EVERYWHERE in the mixer.
TAP and HOLD the knob to move faders up and down.

Sound - I feel the sound is better in ST4 than ST3, cannot say why and what, more open? better clarity?
not sure, but it sounded better.
however, and maybe its fine for those who can have lengthy sound checks, I dont really have that luxury
in my bar gigs, its plug in and go, I did try and balance my tracks with my guitar at home
but when i got to the gig everything changed and honestly, it took me a few gigs
to perfectly balance ST3 with the AUv3 processor (EQ and Compression) and the on board ST3 Graphic,
now I need to load another Graphic, it is not the same and it is quite the mission to get this done, also
because I am not sure how is the audio flow in ST3, is it graphic first, then master FX? other way?
my tracks are good and balanced but now the whole settings changed and it is not going to be sounding good
outright. I get its another app, but it is just me bitching about needing to now find time and space to set up
my whole rig and run through at least a few dozen songs to get the sound right.

bug(s)
every now and again ST4 stops showing the audio meters and at the same time
it looks like on the scrub meter that songs are starting from the middle. they dont, it just looks like i dragged
my finger on that yellow song bar and every song i load looks like that.
close and then open app sorts it.

parts of the app are still super sluggish.
towards the end of a song ill hit the xfade, no response visually and so i think maybe i missed the button
so i hit it again, sometimes a third time even just to find out i did actully hit it but the response is slow
and so now i am xfading 3 or 4 songs it jumped down a few songs, very frustrating, even though i fully understand
the app still must go through more optimization.

I got this BT pedal the chocolate plus, hearing that the irig one isnt working on iOS26 (it does actually)
and i kept losing the connection to ST4, upon checking the pedal was still connected to the iPad

obviously not ST4 related, but if you havent updated to iPadOS26, please DONT
OMG apple what have you done??
I have ST3 and Spotify side by side, one click on those 3 dots on top and done.
what a stupid mission to get it done now. swipe down, try to see those stupid menus now and look what is what
what the hell did they do???

Spotify now after a minute or so stops abruptly in the background or if the screen is off
WTF????????
now i leave the screen on, great so the drunks can go on stage and mess with my stuff. how nice
if anyone can assist with how the hell i can get this to work pls help.

while i am on full bitch mode i am gonna ask again MASTER FX
if only ONE AUv3 and the same Graphic EQ with exactly the same signal path/flow?
this way we only need to balance all the wonderful new multitracks options you gave us.
youve given us an amazing mixer feature but took away a basic function.
if you do this, you wont need mute groups because the mixer already offers that option.

some good stuff:
being able to open the mixer and mid song and still seeing the song list, lyrics, being able to tune the mix
is awesome, most of the gig i kept the mixer open because i knew i would need to mess around
so much (and I have) with master, effects, stems etc.

the app does have a great flow to it, many things feel natural and easy, i think there is more than just potential, i think you are very close.
I think you should try remember things that made ST3 so easy to use, I dont rememebr ever having issues
pulling down or up volume of a stem, EQ adjustments etc, those arent so easy to do here.
maybe some of it is still to be tweaked, it is very good but still not gig ready, I dont think i would want to go through
this stress again.
and after balancing everyting in ST3 now needing to do it (almost) all over again is gonna make me think do I even want this, to need to put all this time in?

Peter it took me 4 days to just assign all my stems to the right busses in ST4. 4 days!! it wasnt seamless.
I know this is a new app but then why can i restore a backup from ST3?

I am not saying go back to the drawing board, I think this app is highly amazing in many ways
and at the same time frustrating.

I dont know if I remember anything else, but this was more and worse than teething pains.
for now I will test at home, i wont put myself through another anxiety gig like that.
it didnt crash at the gig, but it did a few times at home while i was deleting
all my lighting midi commands (gonna redo them all in ST4 later)
clicking on the 3 dots in the editor.
On that note, if i delete something by mistake, how do dismiss what i did like in ST3?? there is no way that i saw and then any change is now permanent???

I think ill stop now, its long enough.
its not all negative, but much of it is driven by me so used to the ease of ST3 and tonight i needed
to make so many sonic changes, play around with the mixer and buss effects so much (Eq work)
that maybe that alone made my evening negative