The astro tracer is a phenomenal tool, well done RICOH/Pentax.
Three shot panorama stitched in Lightroom CC

I use a K-5iis side by side with a K-3 at my local kart track. Both are loaded with the Sandisk Extreme Pro 95mb/s and at the end of a burst I am lucky if the card in the iis has completed writing before the karts come round for the next lap. However with the 3 write is well and truly over and I usually have time to review a few shots before the kart come round for the next lap. The difference in write speed is huge!

I took mine to Skomer Island a few weekends back with the sole intention of shooting the cliche of puffins in flight with a gringo mustache of sandeels. but it absolutely refused to keep anything in focus that was coming towards me. I lucked out with 1 in 5 hours. I did manage to get some flying parallel to me but even then the camera kept focussing on the background even though that was flashing past and the puffin in the scene was the only constant. I had a go with my mate's Canon 70d with an old Bigma 50-500 and was astounded at how well it kept up, even when the birds were a speck in the VF it still nailed the focus and micro adjusted permanently. If my lens/camera achieved focus it would simply stop doing anything, almost like "there you go it's in focus now", but of course the subject has moved in that time and the lens did nothing to reattain focus, I had to repress the AF (rear) button to get it to try again and the whole woeful experience would start again. By the time it had found focus again the puffin had passed me and I might get a shot of its bum. Come on Pentax SORT IT!!!
I have also given up using it at my local kart track for the same reasons. I use the supposedly glacially slow DA*50-135 and it nails focus more times than not, not as good as the Sigma 70-200 but good enough.
The 150-450 is superb, outstanding, incredible at stationary and slow moving objects but anything moving faster than a 3 toed sloth with rickets it will struggle with.
Sad really at this price point. Sorely tempted to jump ship ... not to Canon though

It's a miracle

Thanks Tyone

Not found an issue with mine, It even bests my DA*300 + 1.4x TC. You have to be spot on with the focus though and very still. It's still not great focusing on moving targets when mounted on a K-3
https://www.flickr.com/photos/k_paxian/albums/72157670182307936
https://www.flickr.com/photos/k_paxian/albums/72157666036189960
https://www.flickr.com/photos/k_paxian/albums/72157664155442133

I bought one off here for a workmate's daughter, a white stormtrooper. She loves it, I gave her a Pentax A 50mm f1.7 too and it's her fave lens.
However the dreaded shutter motor failure reared its ugly head and she was devastated. Her dad was none too pleased either. So he set about getting it fixed FOC and succeeded
While we are still part of Europe you have certain rights and goods are expected to last a period of time from purchase. Not sure how the girls dad worded his emails but he used this website to his advantage and Pentax fixed the motor for free.

http://europa.eu/youreurope/citizens/consumers/shopping/guarantees-returns/index...

I can vouch for this, immaculate condition, looks like it has never been out of the box.

But not K mount
Although it was rumoured at launch (ish) but never materialised.

I so want one but at that price he's dreaming. It's a legend of a lens, but that doesn't deter from the fact that it's a very old lens now and doesn't command that price. I've had this very lens on a watch for months and if it gets posted at a reasonable price I may pounce, but until then......