The liner lock is definitely a mixed bag. In some ways it's been a real boon for knifemakers, because users love the smoothness and one-hand opening. In some ways it's been a disaster for actual knife users, because the makers are having a lot of trouble doing the liner lock properly, and liner locks that auto-disengage are epidemic.
The biggest concern with the liner lock is auto-disengaging. The first problem is that many locks don't quite engage the tang enough and/or stick out a bit from the handle slabs. When you grip the knife firmly, the flesh of your hand comes in around the lock and can disengage it outright, or else cause the lock to disengage in use. A disaster.
Another disaster is the angle on the blade tang itself. If not done right, the lock can slide right off. Many liner locks can be made to fail by just putting palm pressure on the spine of the blade. This kind if pressure is often seen in utility use, and a lock failing like this is UNACCEPTABLE. Other liner locks can be made to fail by just a tap on the spine of the blade. Makers argue that such a test is unfair because a knife should not be used as a hammer. Nonsense. First of all, no other lock has this problem. Second of all, if you slam the knife into something, some of the force can be vectored into the blade spine, and act like an impulse force -- that is, it can act like a hammering force that closes the blade. Third of all, knifemakers listen up, if you're going to advertise your knife as tactical, I'm going to damn well test it as if it's tactical. Having the knife get struck on the back of the blade is a low-percentage scenario but a real one.
What's worse, even if your liner lock passes all the tests, it can wear in and someday suddenly start to fail them! I've had a lock that past all tests for a couple years before it suddenly started failing the impulse-on-spine test. You can't test your liner lock once and assume it will be sound forever.
All that said, there are a few makers who consistently make very sound liner locks. There are a few makers who consistently make bad ones. There are many makers who sometimes get it right and sometimes don't. The moral of the story: the liner lock is hard to do properly, even by custom knife makers, who I consider absolutely brilliant artisans and craftsmen. If THEY can't do it consistently, we should look for other lock types.
At this point I'm a fan of lock innovation. The rock lock, the rolling lock, the axis lock, I haven't tested them all. But I'm hoping new lock types will emerge that don't have the liner locks problems, and are easier for makers and manufacturers to consistently do right.
Phew. I think I gotta cut down on the caffeine.