Here's a gripe which: inconsistency in training. I think that, for a long time, I complained about how training does not trigger dreams or other stuff like that, but now, it's... extremely fucked?
Training a power with River jumps time forwards two days, and spawns the player in the inn at 6 AM on the second day.
Training a power with Garth jumps time forwards 24 hours, and then, I believe, puts the PC to sleep, which I can tell because it provides the on-sleep buffs and lets the player dream, while River's doesn't.
Ivris training and Sanders training also cause dreams in this manner, but because Sanders is unavailable after 6 pm and Ivris is unavailable after 7 pm, their minimum required time for training is 38 hours and 37 hours, respectively, while the minimum time for a Garth training is 26 hours since you can have training start right before 6 am on one day, so that when you go to sleep 24 hours later, you wake up 2 hours later. The maximum is, of course, 48 hours, which is around what you'll experience if you wake up and immediately go to train.
Vivianne moves time forwards 24 hours for one of her trainings, but does not cause you to go to sleep after, so you just finish exactly 24 hours after you start and go on your way.
Jin-Jin, when training you in Lightning fist, also just moves time forwards 24 hours. No sleeping, no waking up in the Inn.
Leorah is the one of two trainers in Hawkethorne who take less than 24 hours to train a power with. When training, upon completion of the training, you spawn in the Inn, at 8 am the next morning, rather than the morning after the next morning. However, you do not sleep. This means the minimum time to train with Leorah is 13 hours, and the maximum is 24 hours.
Barney is the other trainer who takes less than 24 hours. Like Leorah, training Prestidigitation spawns you at the inn, at 8 am, but there is no time restriction on meeting him, so you can, hypothetically, have a training time of literally one minute if you begin training at 7:59. Of course, it's not always exactly 8 am, it seems to have a random time between 8 and 8:10 for all of these, but still. He has the hypothetically shortest training time of any trainer, with a minimum of one minute, and a maximum of 24 hours.
Finally, Zo. Zo is the final trainer currently in the game (to my knowledge), and also is the most unique in training, because her sessions don't timeskip either 24 hours ahead or to the next instance of 8 am, and instead you do training sessions. You unlock every power over 7 days, assuming you do the requisite training sessions, repeatedly, and each session takes only a short amount of time. Honestly, it's my favorite method of training since it's actually interactive rather than just a timeskip, but it's also so unconnected to other training methods that I might as well not have put it here. For each individual power, she takes less time than Leorah, but Barney has the undisputed shortest training time.
All of this is to say: It's annoying how some trainers jump you forwards two days, some jump you forwards exactly 24 hours, some just jump until the next 8 am instance, and there seems to be no coordination. Personally, I'm annoyed that the 8 am trainers (Leorah and Barney) don't cause you to gain the benefits of sleep, and also that the 24 hour period non-sleep trainers don't cause you to gain the benefits of sleep, but I definitely prefer them over Ivris, Sanders, and Garth, who take 24 hours and then just auto-hit the sleep button rather than taking 24 hours and giving the benefits of sleep (and access to dreams). And the worst of all of them is River, since his has the downside of being extraordinarily long that Garth, Ivris, and Sanders have, without the upside of accessing dreams and sleep perks activating.