I’ve never seen it done in a match when I’m not the one doing it haha.
Anyways I’ll chime in finally on my thoughts.
U2 is not that good, and I feel use of it should be kept to minimum especially with how powerful overhead to U1 is now.
The only characters I think u2 deserves consideration against are below, I personally use both ultras on every character but Dhalsim, it depends on the player:
Dhalsim - Covers teleports, his fireball, and it makes your downback vs. him basically unbreakable. U1 is good to make comebacks vs. Sim, but U2 can pretty much guarantee you a match if you get it and have a lifelead, so why not?
Ibuki - Stops her most basic vortex and gives you a little more room to breath when you’re knocked down. I still use u1 vs. her sometimes though.
Sagat - Blanka can reasonably build 2 ultras per round absorbing fireballs and you won’t get a lot of chances to get inside and combo to u1 vs. him. Online I use u1 more because it’s hard to reaction ultra a fireball
Gouken - Sort of similar to sim in that u2 destroys a lot of his options. U1 chip also does not work on gouken which is a mark against U1. I think this really depends on the player though. Against flip happy goukens I will use u2, but against ones who are comfortable walking forward I will use u1.
Akuma - Not great vs. vortex, but it can keep him from laming you out when life totals are close. I’ve been using u1 more frequently vs. him recently though, his hitbox is so nice for u1 combos.
Rose - Her fireball is only really useful vs. Blanka full screen. The idea isn’t to actually use u2 vs. her, but just to make your job easy where she has to come and play footsies if the life totals are close. U1 is the better option though.
People might be wondering why I don’t have more shotos, seth, etc. on here. My reasoning is really simple. If you don’t stay mobile vs. those characters you die. Against a good Ryu player if I sit on down back he’s just going to walk forward and force me to hit buttons on his terms or block if I want to keep my downback charge. Seth is just going to dash forward or tanden, and so on. When you deny another character an option I think you can’t just make yourself so vulnerable. Being mobile and having slide at the ready gives you more options than downback does, especially when you factor in the ability to hit confirm into u1 and how weak u2 is vs. safejumps/meaties while u1 is a pretty huge threat on wakeup.