My 2-cents worth on the macro lens is the Tamron SP90mm Macro (the newest version for digital).
I haven't tried the Pentax 100mm Macro, so can't comment on it, but the Tamron SP90 is a classic of over 20 years standing, and is excellent. Not expensive either in the grand scheme of things.
I had the Tamron SP90 on my old Nikon film camera, and took a heap of great shots with it. As a relatively recent convert to Pentax digital SLR, one of the first lenses I bought was the appropriate version of the Tamron SP90.
Highly recommended.
The only other lens I can comment on is the Sigma 10-20mm rectilinear wide-angle. I have this lens as well as the Pentax 10-17 Fisheye. Now I know that everyone's methods and preferences are different, but I find that I only use the Fisheye occasionally for special effects, but the Sigma 10-20 is an outstanding landscape lens. Great lens, and with the PT Lens software to perform perspective correction if required, some absolutely stunning landscapes have been produced by others far more expert then me.
An excellent example, that I've quoted before, is Helga Kvam from Iceland (surely one of the most photogenic countries on the planet). She has now switched to a full-frame Canon 5D, so had to get rid of her Sigma 10-20, but most of the work in her online albums predates the change, and a large number are shot with the Sigma 10-20. Prepare to be amazed at the talent, if you're not familiar with Helga's work, and check out:
Flickr: Photos from hkvam
In particular, check out the set labelled "Your Favourites" - some amazing pics in there taken with the Sigma 10-20, one of the best being this one, taken at the 10mm end:
dawn over the fields on Flickr - Photo Sharing!
Amazing stuff. Just goes to show it's the photographer rather than the lens that makes a photo work.....