And I thought Chargestone Cave was annoying in regular Black and White...that just looked unpleasant.
Trust me it's even worse when you don't have repels. Oh the horror XD
However Twist Mountain is easily the worst cave in this game. It's long, it's confusing, there are tons of trainers, and you'll get hit by wilds every 2 steps if you don't have repels. Chargestone Cave's annoyingness is nothing in comparison. Luckily if you're playing in winter though, snow builds up and allows you a shortcut down Twist Mountain at a certain area. I was so relieved when I discovered that.