Sorry, I believe this is FUD.

Pentax is really no worse than any other lens company.

I have 6 SDM lenses and none have failed. DA*55 f1.4, DA17-70 f4, DA*16-50 f2.8, DA*50-135 f2.8, DA*60-250 f4, DA*300 f4. Of these lenses, the DA*16-50 and the DA*50-135 I have owned for 2.5 years.

See the lens defect page:
http://www.lensplay.com/lenses/lens_defect_results.php

As stated on the page:
•First the survey doesn't sample random users. It samples users who were directed here from one of two or three other websites.
•Second it doesn't sample all users, only those motivated to fill in the survey.
•Third, some people like to mess with surveys and give bogus data. While efforts have been made to detect and eliminate obviously bogus data, it can't all be eliminated.
•Fourth, it's possible that people with complaints are more likely to be motivated to leave their data than those who are happy with their lenses.
•Fifth, there is no differentiation here between cheap Photographic lenses and expensive lenses. You might expect cheap SLR lenses to have lower quality control and perhaps a higher numbers of defects, but on the other hand you might expect buyers of expensive SLR lenses to be more critical and so find more defects!

Now, even allowing for the above, look at the lens defects results. Pentax isn't so bad after all.

Right on the money!

I couldn't agree more, but he does cover this in his "results page":

The data presented here is based on the Lens Defect Survey. No survey is 100% reliable and as someone once may have said 'There are lies, damned lies, and statistics' (Mark Twain quoting Benjamin Disraeli). So be aware that:

•First the survey doesn't sample random users. It samples users who were directed here from one of two or three other websites.
•Second it doesn't sample all users, only those motivated to fill in the survey.
•Third, some people like to mess with surveys and give bogus data. While efforts have been made to detect and eliminate obviously bogus data, it can't all be eliminated.
•Fourth, it's possible that people with complaints are more likely to be motivated to leave their data than those who are happy with their lenses.
•Fifth, there is no differentiation here between cheap Photographic lenses and expensive lenses. You might expect cheap SLR lenses to have lower quality control and perhaps a higher numbers of defects, but on the other hand you might expect buyers of expensive SLR lenses to be more critical and so find more defects!

Very true, but it seems as though it is one of the best of all the brands, according to this survey snippet.

Which proves my point.

This is as it stands at the time of my post:

Survey Results
Note: Values are greyed out if there are less than 300 lenses sampled

Canon lenses - 12002 with 905 defects
The probability of getting a good lens is 92 %
The probability of getting 5 Canon lenses in a row is 68 %

Sigma lenses - 2624 with 579 defects
The probability of getting a good lens is 78 %
The probability of getting 5 good Sigma lenses in a row is 29 %

Tamron lenses - 1300 with 201 defects
The probability of getting a good lens is 85 %
The probability of getting 5 good Tamron lenses in a row is 43 %

Tokina lenses - 428 with 69 defects
The probability of getting a good lens is 84 %
The probability of getting 5 good Tokina lenses in a row is 42 %

Nikon lenses - 2182 with 171 defects
The probability of getting a good lens is 92 %
The probability of getting 5 good Nikon lenses in a row is 66 %

Pentax lenses - 1035 with 77 defects
The probability of getting a good lens is 93 %
The probability of getting 5 good Pentax lenses in a row is 68 %

Minolta/Konica/Sony lenses - 582 with 60 defects
The probability of getting a good lens is 90 %
The probability of getting 5 good Minolta/Sony lenses in a row is 58 %

Other lenses - 841 with 89 defects
The probability of getting a good lens is 89 %
The probability of getting 5 good Other lenses in a row is 57 %

It would seem that Pentax has the best rating at 93% probability of getting a good one.

My FA31 Limited Back focused on my K10. With the K20D and the K7 I can adjust for this with the AF ADjustment feature. I would say that his K10 is Back Focusing with the FA31.

Well, the Tamron 18-200 shouldn't look any worse at simialr sizes on the computer than it did on the K2000. There are a number of possibilities for the Tamron looking softer on the K7 as compared to the K2000.

1) You may need to check for Back or Front Focus. Back Focus (BF) is where the lens has a propensity to focus behind the subject/focus point and Front Focus (FF) is where the lens focuses in front of the subject/focus point.

Test the lens out on a subject with a wide aperture, like f4 and look at your results on the computer. If the lens is showing either BF or FF, then you will need to access the "AF Adjustment" feature which is adjustment number 36 in your "Custom Settings" menu. Follow the procedure on page 121 of the manual.

2) As Pete - iceblinker - pointed out, there may be slight differences in AA filters between the K2000 and the K7 which may have a slight impact on the perception of sharpness, although I am not sue about this. Being a "lower end" camera, the K2000 may have a weaker AA filter and thus would look possibly sharper straight out of the camera.

3) Check your sharpness settings on the jpeg menu in the camera. Sharpness settings may be different in each camera.

I have all 3 lenses, the DA14 f2.8, the DA15 f4 Limited and the DA12-24 f4. What Richard has said sums it all up very well but I will add that I rarely use the DA12-24 f4 due to it's size and now mostly use the DA15 as it is small - doesn't hardly take up any room in the bag and is lightweight - and has the "Limited" look to it's IQ. The beauty of the fixed focal length lenses over the zoom is that they have a closer focusing distance and also have a DOF scale on the barrel, both of which I find indispensible.

It's a stunning lens. Possibly one of the finest examples of any lens maker's art. Read this article:
http://www.luminous-landscape.com/columns/sm-02-05-02.shtml

Congrats on the new lens. I also happen to think it is a fantastic lens.