The round hole is really hard to beat as to opening comfort and first of all security. It is always possible to slide users thumb from the opening stud onto the edge when opening knife not enough carefully or under stress/hurry. Especially if the knife has narrow blade and puts up somewhat more resistance at the first stage of opening.
This is near impossible if opening device is round hole. Since Im rating safety (especially my own one
) at very first place and the comfort (naturally my own again
) at the second the SpyderHole is just right for me!
About improvements hard question...
I cant say with clear cut do I like the hole plus CobraHood more than simply hole. Sure, someone should be completely drunken, drugged and inherently manually handicapped at the same time to miss such combination with his or her thumb... But there are some drawbacks also, for example my Ti-Salsa tends to come from the pocket partially opened because CobraHood catches on the pocket edge in draw. Probably this shouldnt be an issue on tip-down carry...
Kit Carsons
flipper on CRKT M16 and M18 series and Ken Onions
index trigger on KERSHAW SpeedSafe equipped knives (Boa, Chive, Scallion) are at least not slower, not less safe at opening, not less comfortable in comparison with SpyderHole. But can they be considered as improvement I really doubt, they are very different and also not completely snag-free...
Greatly probably this is the question of individual preferences and
entire knife evaluation...