Well after reading the whole thread, I have to say it's the internet at it's best. Many people posting opinions without documentation. My advice on that is, for many of these posts, you cannot know, if what the person says is accurate. People will complain about how fast something focuses, but they may be talking about how smooth the lenses focuses, whether it focuses by and object and comes back, or a hundred other variations between lenses and manufacturers that feel "faster or slower" but may have nothing to do with actual performance. A simple fact, if you tell people one camera is faster or slower, they will experience that, true or not. You you have to get inside the poster's head and try and evaluate their biases. That's impossible to do with any accuracy.
So word of advice to the new. Listen to the guys who have spent time with both Canon and Pentax and can talk about both in positive terms. Someone who takes a modern camera, any modern camera, and start talking trash about it, has other issues. IN photography, your point and shoot is just as important as your SLR because for a lot of photos, you don't have time to set up. And for a lot of issues, it's not about the camera. There are simply stated, no systems designed to give you perfect pictures every time. No company has the time to sit down with every photographer and look at how he shoots, and customize a camera for his or her shooting style. To some extent, being a photographer is learning to shoot with the equipment you have.
The original poster would have you believe that if you buy a Canon, you will be able to get a higher percentage of fast moving shots in low light.
My first question is, show me some evidence this might be true?
The second, for the guys who claim something is critical, put up an example. Now this is tough for people, it's easy to have an opinion, it's hard to put up the data that make you think that way, because someone else may have a different interpretation of what you perceive as a problem, and my even have a simple work around based on camera settings that you never investigated. You could end up looking dumb, it's happened to me many times. But if you don't take that chance, you don't learn.
So you have to take a chance. I have a sequence of shots of one of my border collies task in burst mode, hand held, with every shot in acceptable focus with my K-x and a Sigma 70-300 macro 1:2 macro.. those pictures say more about the K-x's (and I assume later Pentax's. than almost anything I've seen here.) I can't post them right now because my wife has the computer we do our PP on, but I'll post them later. These shots were what I use for my reference of what my camera can and can't do. And I have to say, the negatives on this thread are about one function, low light auto focus.
A lot of the statements on here would suggest that my camera can't do what it does. That I find offensive. If you want to discuss stuff fine. If some guy wants to claim his whole photographic experience revolves around auto-focussing in low light, that's fine too. But recognize, he's talking about .05% of my photographic experience.
So what I want to see is a side by side comparison of a group of shots showing the shots he got with someone got with a Canon, and other shots someone got with a Pentax, and clear examples of why one is better than the other. Even if there is a difference, I'm guessing it's a difference over very small range of specific lighting conditions. And I'm also guessing that someone has a workaround that negates the difference. I am really tired of the opinions of writers who comment on minute differences between cameras as if they were in some way meaningful facts.
Long story short, my Pentax works fine for me. Does it take every picture I want to take, no it doesn't, but neither does any other camera. I see pictures I'd like to take in pitch blackness, I see pictures I'd like to take of birds that are moving faster than my hand and eye can track. I see pictures in impossible lighting conditions. I see pictures everywhere. There is no camera that can take every picture I see. So if someone says, oh, you can't take this or that picture with a Pentax, the first thing I want to do is go try. Just because you can't doesn't mean I can't. The second thing I want to see is that picture taken with your camera of choice. Because half the time when I see those pictures I just look at it and think, "that isn't a picture I care to take". Whether that be lack of interest in the subject or style or whatever. I love looking at the pictures on this forum, the variety and originality, but, as much as I like looking, there are many I have no interest in taking myself. And it would be a waste of money to buy a camera because that is it's strength.
And the thing is, I would feel the same way if I owned a Canon or a Nikon.There is going to be a learning curve with every camera. When you jump systems you really have to consider how long and if you're willing to spend the time t become prfixcient with the new system. If you didn't have time to read and understand the manual that came with your original system odds are, you won't do it for the new system either.
So to answer a previous post, yes, saying "If Pentax doesn't do this and this I'm switching to Canon" is childish, and there are a number of reasons why. First to make this statement, you have to admit, you bought a camera that isn't suited to your shooting needs. It's not up to Pentax to make a camera that suits your needs. It's up to you to make sure you buy the camera that best suits your needs. If you didn't do your research, don't blame Pentax. That's not their job. Do you really think it's Pentax's responsibility to put out ads that say, "if you want quick focus in low light, and you want to be part of a herd of people who believe their camera is best for that.. buy a Canon or a Nikon." To expect that is naive to the point of being childish.
Second, the OP's perception that Pentax should care about his complaint.. who knows what Pentax is thinking about, what the goals of their engineers are, is also childish. IN putting a sensor and software in the K-5 that increased the Dynamic Range 2 Evs, Pentax has done exactly what I would have wanted. And as another poster pointed out, that's going to help low light images. Assuming we all will be sympathetic to what he wants is also childish.
His post is the equivalent of "I'm going to take my football and go home." And the answer of mature people is to smirk and say "Well go then." Don't buy in to the perceived emotional black mail. And the thing is, maybe he would be better with a Canon system. But, how is that relevant to me? For me, and thousands of other posters on this site, what he's proposing would be stupidity.
Telling thousands of Pentax users you're going to switch to another system is attention seeking and ... childish.
Despite that there have been some great posts along with the usual drivel. SO I can thank the OP for the original post, but my question remains.. how old are you?