Originally posted by RUSBoris So basically can you say something to encourage me to stay? Are Canon lenses the same way on the lower end? And is the focusing problem a body problem or lens problem?
In my limited experience of Canon lenses, the auto focus, even of their kit lenses is better than Pentax when used on their higher end bodies, however I have friends who have low end Canon bodies with moderately high end lenses and they complain about the focus precision of their kit, particularly the long lenses where it is more noticeable if there is a significant problem. Focus speed is comparable on some lenses and much faster on others.
In my experience the Pentax auto focus on K10/20D is much fussier than on Canon and so takes a little longer to focus but gets a spot on result. All that may be about to change with the two new bodies currently being released which seem to be a major catch up. Any camera/lens combo can miss focus in low contrast or poor light settings and shift through it's entire range.
The Canon 50mm f1.8 you mention is cheap because it is cheaply made. The Optics are OK but the construction is mostly plastic. One friend has broken three of them in four years. The short focus stopper just wears out and the focus ring is pliable enough and the focus motor strong enough that the lens just pops itself apart and the end elements end up on the ground. However he doesn't seem to mind as he says it is cheap enough to just keep buying them and then he never has to bother about cleaning them either.
As you bought the Kx, I guess you don't particularly care about the big advantage that Pentax holds: Affordable Weatherproofing. That is the main reason I am sticking with Pentax.
Whatever brand of camera you have, don't feel tied to their lens range. Tamron, Sigma, (Tokina) and Samyang produce some excellent affordable lens for all major mounts. The Pentax range has great build quality and some nice features like the best focus clutch system available. I agree that some are overpriced, but most are designed to last indefinitely. Cheaper lenses (possibly including the "L" series that you probably have) generally are not.
So no definitive answer for you. You have to decide which features are important to you.