I have been carrying pocket clip knives since 1981 and for the life of me I cannot undertand why anyone would want to or prefer tip up carry (unless your first 10 knives were made tip up and you just got used to the flaw). Tip down assures you won';t get cut and deployment is faster and easier. Not that a .02 of a second make a difference. just why make things harder and also risk the cuts reaching into a pocket of a detent spring or looser pivot screw when a tip down carry you won't have to worry about that and where to place the knife against you pocket ect ect ect..
These threads always appear because of the problem with tip up carry. I am sure there are lot more accidents that people do not report and see on a thread everyday that do not post. IMO tip up is a poor design and nothing else.
I own, and have carried dozens of tip up carry knives, in both front AND rear pockets, as well as a couple of other configurations, and have NEVER cut myself reaching for it. Maybe I'm in the lucky minority.
Has the knife ever partially opened in my pocket? Maybe a couple of times. But if the knife is pushed back agaist your pocket, the only thing you might cut is your pocket.
As for speed, the fastest knives (those with a "wave" feature) are actually designed around the concept of tip up carry.
Personally, wave or not, I tend to draw and open as fast, if not faster, with a tip up carry than I do tip down. That said, I do have relatively large hands.
When drawing tip up, I tend to pinch the bottom (clipped portion) of the knife between my palm and ring finger (or depending on clip style, I'll index my ring and middle fingers against the clip), while also indexing my thumb at the pivot of the knife. As I clear the pocket, I then obtain a full grip, where I'm already in position to use the thumb stud.
For tip down, I pinch the pivot between my thumb and index finger, and as I draw, rotate the knife into my palm for a full grip where, again, I'm able to use the thumb stud.
For me, one method isn't any more difficult than the other, I suppose I'm just used to the former.