well, first of all i'll share my experience about the new camera..
Ergonomically it's almost identical, however small changes in battery compartment door and memory card door, and somewhat different grip.. makes it better ergonomically. that's a good thing.
built quality, did not notice any change. do not know the technical data, to me, seems as good as K10D.
AF speed. it's a little faster. in good lighting and in poor light. judging spontaneously it's 1/5; 1/6 faster.
many aspects in main menu are expanded, improved, some features added.. these are all good things.. among which intervalometer is very welcome feature, more options with raw button, more options in custom menu, custom images modes are nice to play with, expanded dinamic range, and some other..
live view.. well it's not good a all.. but it's usable. you have to learn a bit, be a little patient, and it becomes something, like in primitive compacts..
however, when shooting in live view, you cannot change any sattings.. or I haven't figured it out.. it's a very dissapointing.. I tried shooting in Sv mode, and couldn't even change ISO.
also, when Image stabilisation is On in liveview some kind of noise is audible.. you can turn it off, by switching SR off.
so far so good.. well in a few words, Liveview on K20D sucks, but it's better than nothing.
I have sigma 17-70mm and AF on K10d in good light it's slow but usable in poor light it;s useless.. however with K20D in good light it's quite fast and responsive, in poor light it's slow, but usable..
better, but not good enough.
what about image quality and noise... to be honest, i expected more.
with K10D i could freely shoot up to 800, and for the weddings i used even ISO 1250. and had pleasant results, later could minimally remove some noise with software, and pictures looked good
from K20D i expected to shoot freely up to ISO 2500.. however the results dissapointed me a bit..
800 ISO is clearly better on K20D, 1000, 1250 and 1600 arguably better.. K20D sometimes you can get good results, even at 2000 but sometimes 1250 seems worse than K10D. that's annoining. K10D is stable what concerns noise control, K20D can sometimes give very good results, and sometimes it can spoil your mood..
i set Noise reduction on Weak. because when I set it on strong, too many datails were lost even a t ISO 1000.
what matters white balance, it does a little better job than K10D on auto.
we all know that on both of these cameras, you have a lot of freedom to use custom WB, so if to use custom, both are equally good.
the most dissapointing was continous shooting. it's not that stable, not that fast and not that pleasant as of K10D. i never actuall y used prolonged shooting continously, however it was nice to know, that i have such a posibility, even at 3fps, but until the end of the card, now, after 7-10 shots, it starts jerking.. it's annoing..
what about that burst shooting.. 21fps..
it's a joke.. maybe you can find some specific situations, where it would be usable, but right now, i think it's useless. it let's you to shoot.. for not more that 4-5 seconds.. and it stops.. then it saves the images.. for a minute.. and you cannot do anything..
if it at least could go until the memory card is full then i could find some uses but now..
overall.. it's an upgrade. i already put K10D on sale.
next week, i'll get Kit lense 18-55 II and if AF on it will be faster in low light, i will sell K10D with my "higher class" sigma 17-70mm.
considering that SR is improved, Sensor Dust improved, AF imroved, many other features, added and improved, slightly better ISO performance it's a good bargain. I bought it used with a guarantee up to next fall.. with a spare battery and an infrared remote.
now the question..
I heard that it also has some tracking autofocus.. as I understand it is used to follow the subjects..? I would appreciate any comments on that..?