I use the twisted grip and I don't mind talking about it. I have experienced some pains as the result of using the twisted grip which have kept me off of the pole for days at a time. Part of this is the physical awkwardness of the position itself, and part of it has been negligence on my own part. But I have also caused myself certain pains by doing other moves like the cartwheel mount. I think any move can be dangerous or harmful for someone whose musculature isn't prepared for it in terms of strength and flexibility, and even the very strong and very flexible can hurt themselves by trying advanced moves without being warmed up adequately first.
Here are some things I like about the twisted grip. I will preface this by saying I only like twisted grip after I am inverted. But once I am inverted, the grip feels more natural and seems less taxing on the wrist and elbow of my top bracket than does the split grip (or cartwheel mount). In addition to this, it offers a lot more control over the aerial movement done in inverted holds. Also, I feel like the twisted grip allows me to hold my torso straighter without the odd sideways-bowing that I have found characteristic of the split grip in inversions. Lastly, I really like that this grip offers the ability to do very slow and controlled lifts and dismounts, instead of leaps and falls.
Now here are some things that I do not like at all about the twisted grip! From the floor, it feels very awkward and can be painful if I am not very precise about my hand and body positioning. Also, pushing off into a slow lift, I have found, puts a lot of strain on the shoulder of my lower bracket (usually left for me) which can leave that shoulder hurting for a couple days (after all, a body is a lot of weight to put there). Further, if I have to shift around too much to get myself inverted in the twisted grip, I find that there is some discomfort for a day or two following behind my right shoulder blade and on the right side of my neck.
I do feel that most of the problems that I have had using the twisted grip could have been mostly alleviated though, if I had been fully warmed up before attempting to do any twisted grip handspring work. Also, whenever I do strength training, I use the Y.T.I. exercise formula that is posted in Veena's video. My friend panda (squishypanda9 who just joined the site today) has been doing that exercise and also Veena's wrist/forearm exercises with me, and I feel much safer when I'm on the pole knowing that I'm using Veena's advice to strengthen and protect some of my very vulnerable muscles and joints. And I've been on enough forced sabbaticals from the pole to realise that I'm just not going to get away with performing demanding pole moves when not adequately warmed up. And if I weren't as stubborn and sometimes dumb as I can be, I would have learnt the first time.
All that said, I learned all of the other grips before I started trying to work with TG. And I fully agree with Veena that this grip should be done from an invert before attempting the handspring. Even though I use the handspring, I still really enjoy going into the twisted grip from a "princess grip" shoulder mount. Once you get your legs on the pole, you can drop your lower bracket, and voila! You're in twisted grip and can butterfly, aysha, or whatever. I like doing inverted bodywave in twisted grip, and when I do it makes everyone at work go crazy!
I am not overly fond of the current TG obsession that's going around right now. It almost looks like its a requirement in order to stay competitive, and I think that's too bad. There are so many beautiful and challenging moves that can be performed on the pole without having to use twisted grip, and most moves that can be done with this grip can be done with other grips. Handspring "lifts" can be done with true grip although this may take more strength and more training. I presently cannot "lift" into anything with that grip, but it has to be possible because its been done in every Chinese pole performance I've ever seen. The straight edge, aysha, and jackknife, can be done with the split, forearm, or elbow grips. I'm sure that if I practiced a little more I could get an inverted bodywave with elbow or forearm grip... and actually after watching this thread, I'm sure I really ought to work on that. I agree with Veena that TG isn't for everyone, and for myself I have found that I can only use the TG handspring in moderation unless I am just in the mood to do some suffering for a day or two to follow. I have a suspicion that the need for moderation in TG may be a universal one, but each poler knows her/his body better than I!