I switched after 1500 hours of regular attack direction, it's a pain in the butt and you'll feel like a drunk retard for a few days. After two weeks I could chamber again, yet after two months I still have the occasional reflex chamber that makes me do the old move, which doesn't exactly work anymore.
Reason I switched is because Senni_Ti always pulled of those turn hits, which look cool and actually confuse a lot of people. He did a 360 during the sideswing animation and hit you, which I couldn't do with regular. Because for example with a right swing, you first have to look right, then move your mouse all the way left, which is too slow. With inverted it is one fluid and natural motion, a really cool move with the 1h rightswing.
Normally with an attack you have to look away from your opponent to start the attack, and then look back to him to hit him early in the animation and not at the arse end. Ofcourse you get used to this and you do it automatically, but its still slightly slower than with inverted. I can hit someone with a right swing and then do a really fast 1h leftswing hit to the face. 2 hits that just consists of two quick mouse swipes.
One big disadvantage though is that normally chambering is basically doing the same as blocking, but with LMB combined with timing and angling. I learned chambering by just looking at the incoming attack and pressing LMB, which is sort of a logical next step after you learned good blocking. With inverted you need to look away from the incoming attack, which makes it hard to maintain the proper angle. I'm still very bad at chambering with the 1h rightswing, which was always harder than the other attacks, but I'm quite sure I used to be better at it. For all weapons chambering with the leftswing is a lot easier than with the rightswing for some reason.
Also nowadays stabbing from high to low works very well at close range with long stab weapons, it's kinda useful that with inverted you look up to stab.
Overall it's pretty minor, I like just having an unusual looking playstyle and doing weird stuff that looks cool visually. It's not necessary at all, if you really don't feel like struggling for two weeks then don't do it.