A nice preset lens is a good way to adjust aperture during video without any clicks.
(I'm thinking here of the ones that have two aperture rings like the silver/black Takumar 135mm.) You would have to go it fairly slowly for the autoexposure to keep up without being distracting.
The 24p annoys me. That standard was created many, many decades ago due to mechanical constraints. It gives a "look" - a somewhat stuttery look, but some prefer it in the same way that some people prefer film grain over no grain, or lens flare over no lens flare, etc... it's taking a negative and turning it into a positive.
Until the advent of 120hZ Tvs, we didn't have the ability to view 24 fps videos at the correct frame rate. NTSC folks had 3:2 pulldown and PAL folks had the dreaded "PAL speedup" where movies would be shorter and the audio pitch increased (the latter lesser so with more modern technology.) 30 fps offers native viewing speeds on NTSC displays and PC monitors (most of which run at at least 60hZ.)
Now, one of the things that I love about Blurays is that the movies are generally encoded at 24fps so when I watch on my 120hZ TV, I get a perfect framerate (24fps x 5.) So I like 24 fps when it's appropriate (and I don't have the TV "smooth it out" by interpolating frames), but I have no interest in creating new 24 fps content when 30 fps is smoother and plays in more places correctly.
If I lived in a country that used PAL, I'd probably be quite happy with the 25 fps of the K-5. But I'm not. I want 30 fps, which I why I still shoot in 1280x720, just like I did with the K-7. IMHO, 24 fps is only worthwhile if your content is going to be converted to film and run through a projector or if you really want the slower, more stuttery look of 24 fps.
I know there are plenty of people who disagree with this, but those are my opinions on the matter. So far, only Canon has offered 1080/30fps on their DSLRs, which is probably part of the reason why they're popular for creating TV content (among other reasons, like there not being any serious video DSLR competition, especially in the FF world.)