I've been using Kleen Kanteens for a few years now, and love them. About the sport caps...they work pretty well, but there is a trick to them. If you look closely in the photo that you linked, you will see 2 whitish "dots" on the base of the cap near the spout. These are the valves that allow air to enter the bottle while you're drinking water out of it (necessary, since as you noted, you can't squeeze the bottle). Through trial and error I learned that if those dots are pointed down (i.e., towards your chin) while you drink, you will get sort of a gurgly, spurty type flow (because inflow of air through the valves is interrupting the flow of water from the bottle into the spout). However, if you aim the dots up (towards your nose), it's a much smoother flow (more like you get out of a conventional bottle. I do have one cap that for whatever reason I can't drink out of very well. I'm not sure what the problem is with it, but I mostly use the screw-on caps anyway (I don't use my bottles for riding because I don't have bottle cages on my bike, and because I use my Camelpak), so I've never done anything with it.
Also note that you have to suck on the sport top to get anything out of it. This is how I drink out of sport bottles anyway, so it's not really a problem, but if you're the type that likes to pour the water in your mouth, it's not going to work very well for you. Same goes for using the bottle to pour water on yourself...water will come out, but it doesn't come out very fast, and you kind of have to shake it.
As far as the kid spouts go...I've never used them on a Kleen Kanteen, but they are the exact same valves that we used on our kids' baby bottles when they graduated from bottles to sippy cups. I drank out of them a few times and while they do work fine, they have kind of a slow flow. I think they really are meant for very young kids.