I can say I have only watched a couple of 24p movies on an TH-58PZ800U as that is the TV my neighbor had when I made my final choice to go with Panasonic and in the movies I did see I could notice no "flicker", that said there is enough traffic (messages) on it to make it hard to igore the topic, so I agree that it is worth investigating.
I have the TH-58PZ850U so my and have never noticed anything but a stunning picture at 24p or 30p.
For reference 24p just means 24fps (frames per second), many Blu-Ray movies are now released at 24p as it is supposed to be more theater like or some such artsy craftys thing as 30 frames per second which is/was the standard NTSC frame rate. I have Blu-Ray discs in 24p and 30p and can't tell the difference but I guess I am not a videophile, they both look great to me. That said, if the picture flickered it would drive me nuts.
For further reference I have seen a lot say that after burn-in or running at 48Hz they have no flicker, I have seen posts that say they notice the flicker no matter what and before and after calibration. So the most I can gather is one message I read where the guy said it could mostly be the sensitivity of the viewer, distance from the TV, ambient lighting, the kinds of movies they watch, etc...
First some perspective on cost, consider most people keep their primary TV for 5 years (60 months) or more, the difference in cost in a 3,000 set and a 2,000 set is 50/mo @ 3,000 or 33/mo @ 2,000, a 22 buck difference for something you are going to get a lot of use of.
Everyones economics are differnt but there are places to look for that best price possible and places not to, and for me TV's are not one of them, it is a long term investment that you will want to be happy with for 5+ years, and forget about selling it used even the next day if you don't like it, you will take a BIG hit.
OK, putting money aside for the moment, I almost always suggest that people with the latest available when it comes to electronics, saving even a grand on a TV you are unhappy with seems like a no brainer to me, it is no save at all, just 1000 bucks less to be frustrated...
So I would be looking at the latest Panasonic's, read the professional reviews as well as the consumer reviews at places like BestBuy, Amazon, here, anywhere you can find them.
I have noticed for example the highend Panasonic's just one model year later than my have 10,000 higher contrast ratio 40,000:1 as mine is 30,000:1 native, they have nearly twice the moving picture rate, now at 1080.
I do not regret for a second the set I have and will have for at least 5 or more years, but if I was buying today I would be getting the latest with the top specs and reviews I could, knowing that each year they are going to likely just get better, so start with the most you can get and/or afford.
The last thing on perspsective is just how much these things are important to you, personally I would not buy a TV if I read a number of reviews (professional or personal) that noted a consistent flaw or issue, on the "where there is smoke there is fire" theory.
Last note, the last 10 or so Blu-Ray discs I got were all 24fps so it seems clear that 24p is here to stay. I know this was not a detailed technical review, it was just to put your overall decision in a broader context, or pun intended, to say look at the big picture in how you decide as well as the detail.