I used to have one of these but sold it a while back as I rarely used it. The small size was slightly useful (I used to take it with an MX for hillwalking trips) but optically, while ok, it's no star.

I started off on macro with extension tubes and then bought a cheap Vivitar 55mm F2.8 Macro which goes to 1:1 and is surprisingly sharp. The only downside was that it's manual focus (although that's not a big deal with macro) and it didn't have a "A" position so it didn't work quite as well on my K10D as it did on my DS.

For that reason I bought another cheap macro lens, the AF 100mm Cosina, and I've found that to also be a decent performer. It's noisy on AF (but reasonably fast), needs an adaptor to go to 1:1 and is perhaps not quite as sharp as the 55mm lens - however it's very, very cheap for a proper AF macro lens and is a good choice if you're not doing a huge amount of macro. It's also small and light so easy to find a corner for in the camera bag.

I had a 24-135mm F2.8-4 and while I liked it as a general purpose walk-about lens on a film camera it proved not to be anything like wide enough on a DSLR so I eventually sold it.

My walk-about lens now is the 16-45 F4 which I've found to be excellent. Yes it's somewhat short at the long end however I find that less of a problem than having the lack of width at the wide end. Often these days I pair it with a 70-300 APO Sigma and while that does entail a far amount of lens swapping I've not found that to be problematic because using a slingshot bag makes access to lenses fast.

The 135mm F3.5 pictures mentioned earlier were some of mine. The lens I have isn't all that great - I've had a few no-name 135mm F2.8's in my time though and they've all tended to be at least reasonably ok for sharpness but sometimes without the best of colour renditions (perhaps less of a problem with digital than with film).

A Pentax 135mm will definitely be a safer, if more expensive, option however make sure you go for one that has SMC coating.

The lenses I use most on my DSLR's are the 16-45mm F4 and Sigma 10-20 - either of which would be good upgrades/additions to your existing lens. if you're primarily interested in landscapes then the Sigma 10-20 would be a very good choice.

As well as the quality difference between the 18-55 and 16-45 (which is very significant - certainly for the mk1 18-55) it's also worth noting that the difference in the field of view at the wide end is also very significant. 18mm (equivalent to about 28mm with film) I usually find not quite wide enough where 16mm (equivalent to about 24mm) I find a very useful focal length.

I've had two of the mk1 18-55's (and still have one of them in a cupboard somewhere) but haven't found either to be particularly useful however the 16-45 I find I use a lot.

The HK to Macau jetfoil, seen on my morning ferry commute from Lantau Island to central HK.
Not absolutely sure about equipment but probably Z1p, Tokina ATX-Pro 80-200 F2.8, Provia.

They're somewhat pricey however they do have a pretty good range of stuff in stock, including K and M42 mount lenses.

K10D, Sigma 70-300 APO

K10D, Sigma 70-300 APO