[GEli]

I don't think this is a great choice for a walk-around lens, particularly if space is a big issue. With space being an issue, I'm assuming you aren't going to have a tripod on you when you're walking around with this lens. I also know that with a lens this slow, extended fully you will definitely need one to get any sort of useable image. This is assuming the lens is perfect aside from this aforementioned problem -reviews seem to indicate this is not at all the case.

Might you consider a slightly shorter zoom (both range and minimum length)? The Pentax DA 50-135mm f/2.8 is a really nice lens, though slightly more expensive (~$900 USD). If you're looking for something cheaper, the Pentax 18-55mm f/3.5-5.6 is actually a really well built lens for a kit lens, and really reasonably priced. If you were willing to buy two lenses, you could use this as your walking around lens and get a separate, longer telephoto zoom (or even a telephoto prime!) for special occasions when you have access to a tripod and want to do some work with a longer lens, all while remaining within a reasonable budget.