Haven't had any problems with focusing. I tend to switch to manual focus quite often btw (closest or fix focus at approx 3-4 m).
It might be that your stock camera can access more features than 3rd party apps also.
Most of the good camera apps load in about the same time.. How much time are we talking about in your case?
(Try "Manual Camera", "Shoot" or "FV-5" if you want a few that loads quickly)
Sometimes the camera is messed up and that will only be solved by a restart. Low battery also seems to...