I've got the 135-400mm F4.5-5.6 APO Sigma and it works OK on digital.
Even the Exif data gets picked up (on a lot of lense it doesn't).

PhotMe identifies the exif as:

SIGMA 135-400mm 4.5-5.6 APO (or SIGMA 170-500mm F5-6.3 Aspherical RF APO)

which is OK, it rarely id's just as one lens.

If it's not sharp at f/11...... what's it going to be at f/2.8 Ha!! Ha!!

Bjørn the Exif data is showing 35mm for shake reduction, which won't be helping. Try a shot also with no shake reduction, also try to get 1/250th sec. exposure. It's been reported here and elsewhere that the K-7 suffers from shake at around 1/125th. The K20D doesn't but just to be safe 1/250th with SR OFF would be safer.

For any lens tests you need to take the shot at least 4 times and then pick the sharpest of the 4.

That's a massive improvement. I didn't think you would get rid of all the blue/purple cast, but you have

The 800w pic is also a lot sharper than the forum reduced one which was showing jaggies around the outline of the gull.

It looks like a dirty lens to me, probably the rear element. Just give it a good cleaning and try again.

It should be better with a clean, but I would be surprised if it's as good as the 18-55WR (same as Mk.2) I've yet to see any old WA lens that's as good as the Mk.2 Kit Lens or even a good Mk. 1.

The "Unofficial Pentax Collector's Starter Page" lists it as a separate model

The bad news is that it's probably the most expensive K mount camera to buy in mint condition..... then there's the motordrive..... Ouch!!!

That's the way to get a GOOD PRICE for an SFXn CAMERA!!!!
THROW IN!! a FREE LENS!!

Nice set, but I wouldn't call it complete without the
Top Model the K2DMD

Sadly I never got round to owning a K2DMD either

It was actually on the BBC News site. Very funny

If your intending to do bird photography. Pentax don't make a 100-400mm zoom and the Canon one is a bit of a cracker I think there were two versions and it's the later one that they all rave about even though MTF tests on it don't look that bright. Your nearest option in Pentax glass would be the DA* 300mm f/4 or a Sigma.

Nice shots I like them all.