This has actually happened to me. Not when using an SLR, but when I used a point-and-shoot once. The peak of my cap peeked into the top of the frame. I've just checked with my 18-55 kit lens on the K10D and it just might occur on that lens at the short end.

They would be very dark! Polarising filters alter colour too, ND's are designed to have minimal impact on colour. You might get some strange effects from the polarisers as they rotate and go into "extinction" (total opacity)

Each lens has it's fans. I haven't heard anyone complain about either lens. The 105mm will give you a bit more "stand off" distance from bugs, so you won't scare them (or them scare you!) as much!

If you mean this http://tinyurl.com/2vvxft then yes it is the newer version.

My images in this thread https://www.pentaxuser.com/forum/viewtopic.php?t=4291 were taken with the Tamron (the earlier one, not the newer "designed for digital" which I think is designated "DI". I like it a lot and it I think it was worth the 80 quid or so I paid on evilbay.

I'll put in a good word for the Tamron 90mm SP. They have a newer version specific to digital cameras, but mine is an older one which I picked up for £80 on evilbay.

I use the Organiser in Photoshop Elements. It builds a thumbnail catalogue and you can apply various tags to pictures, then filter the view of the catalogue by those tages. It also makes it easy to archive them to disk (CD or DVD), keeps a thumbnail online, and prompts you to put the disk in the CD/DVD drive when you try to open an image that has been archived.

Also when I first transfer the images from the card reader I have a folder structure along the lines of My Pictures > Year > Month > Topic or Location

Aw Liam, did you have go go and blow my cover as an expert (google/wikipedia) user?

Autofocus works by looking for contrast changes in specific strips of pixels (AFAIK), so in low light you are not going to get much contrast in those strips, therefore autofocus wont't work in low light. It's not a pentax thing nor a K10D thing, it's a limitation of the way such systems work. If you have a flash unit such as the AF360, there is a red illuminator which throws a grid of red light onto the object to allow the AF to work in almost totally dark conditions.

If you team the 18-55 with the 50-200mm you have a lightweight walkabout system that covers a fair range of focal lengths!