Here is the proof again, with photos shot at the same time on a test chart. The remarks made by the OP are clear and self-explanatory:-
http://forums.dpreview.com/forums/read.asp?forum=1036&message=36997087
For quick reference, below are the directly linked pictures from the DAL and the DA II:-

(Above: K-x + DAL 18-55, Click to Enlarge.)

(Above: K-x + DA 18-55 II, Click to Enlarge.)
And, quoted, for what the OP observed (and it's so obvious indeed):-
"First, the DA 18-55 II lens. Note the better edge and corner sharpness compared to the kit lens supplied with the K-x, the DA L 18-55...
The image below is from the L lens, and is not corrected. The two correction functions don't help to correct edge focus - well, if they do, it's not noticeable in my images. I tried all variations.
Even the centre focus drops off towards the edges. Oh, and it's even worse wide open. I'm really trying hard to be nice to Pentax here... "
In short, those newer "plastic wonders" of Pentax could suck! And that all depends on your luck, no wonder! :-( ;-> And afterall, the Pana delivers the best result!
"The image above was auto-corrected in cam; the two settings take around 5 seconds to process and correct for curvature and CA. This slows the camera down immensely, but produces a square, almost error-free image."
"Panasonic get criticised by many for including geometry and CA corrections in-camera - they are applied in every shot. The wonder of all this is that it takes no time at all, in a Panasonic (not 5 seconds like a Pentax), to process these corrections."
As I also have the Pana GF1, I can firmly tell that what that guy says is true!
Some brand defenders would yet argue that the K-x is not the uppermost model of current Pentax DSLRs, so they should see what a new K-5 user reports on the same issue, below!
K-5 Continuous Shooting Does 3 Frames Only! If and When..
Read Also:-
Standard Zoom Mega Shootout! (DA Vs FAJ Vs DAL Vs SA Vs FA!)
(AF) Lens Matching with the Navy K-x
j viviano · 746 weeks ago
"The series II is not as sharp wide open for a very good reason which I will reveal in a few weeks' time when I do my series on lens testing."
"Most on this forum know that DA L has little better optical quality than DA II series particularly in case of 18-55mm kit lens."
http://forums.dpreview.com/forums/read.asp?forum=...
oops ;) I wonder how you could have made THAT mistake
RiceHigh 110p · 746 weeks ago
guest · 746 weeks ago
why do you stick with Pentax again? what's the least, most minor positive attribute that offsets the worst things about Pentax that makes you stay?
RiceHigh 110p · 746 weeks ago
Why I am still using Pentax? Just forget about it, you will not be interested and will never bother to know and believe what I tell or think. For those who knows, they have already known and will know - if they are not yet such a follower.
j viviano · 746 weeks ago
We do not treat Pentax like a religion... but you, on the other hand, are leading a very Catholic crusade against Pentax and it's pagan fanbase ;).
guest · 746 weeks ago
Pentax digital bodies have been improving (albeit at a slow pace) but you still cannot accept or acknowledge that.
And yes, I'm interested on what keeps you with Pentax. So I can understand why you are still using Pentax despite all your criticisms. Who knows, it may be a reason why I should stay also :).
syam · 746 weeks ago
Ok Ricehigh noted but any contrary argument you make, will be considered moot?
Coz I can easily say that the lens designers for the Pana and the Canon or whatever, are lazy that rather than correcting the lens within the lens design itself they used software to do it for them.
In this case u seem to be supporting the lens correction via software so in the future I expect that should Pentax implement this further, I expect that any arguments from you against Pentax's implementation to be invaild
RiceHigh 110p · 746 weeks ago
The second fact is that the in-camera lens correction of many other current cameras by other makers are carried out instantaneously without catching the attention of the users but still do the job. So, why bother if I do not need to stand here and wait for our Pentax DSLRs to do the job for 5 seconds or so (and would miss the chance for taking another photo and then another!)?
I have not even bother to quote in my opening post that the 5-second software corrected image of the Pentax plus kit lens is worse than the zero second software corrected image with the Pana kit, which has actually also been commented by the OP.