camera change

Where does it say that this new DC motor is brushless?

Good one, i don't think it's the DC motor they talk about in here link

Just another new type of lens motor which uses the same contacts (between camera and lens) as SDM, so won't work on the K100D.

Does it not have screw drive capability as well?.

Nope. Or at least, not according to SRS and the Other Forum's lens specs.

The Sigma 18-125mm DC has come out in two flavours, f/3.5-5.6 {May 2004} and the f/3.8-5.6 model {Jan 2008-current}.

So really it might depend on which you have/get, according to DPreview below only the latter comes equipped with Sigma's inbuilt HSM (High-Speed-Motor) for auto focusing, even in their Pentax-K mount ones, which can be a good bonus to have.
http://www.dpreview.com/news/0405/04052101sigma18-125.asp
http://www.dpreview.com/news/0801/08013107sigma18125.asp

Fwiw: I own one of the 3.8 HSMs, so be warned, any S.18-125 is often much-maligned by 'experts' for it's alleged low PQ.
Not being an 'expert' though I can honestly say I'm fairly satisfied with mine. Pix look decent enough for the money (was cheap-bundled with a new K-x anyway), and for its quiet and quick-responsive AF. Also, what a great walk-around size it is - like you mentioned.

Here's one of many reviews on the earlier 3.5 just in case that's the one you're supplied with:
http://www.ephotozine.com/article/Sigma-18125mm-f3556-DC-4598

And here's an old K100D + S.18-125 combo brief reviewed:
http://www.dpexpert.com.au/archives/2006/10/_reviewpentax_k100d_dslr.html

.R.

just checked and the camera comes with the 18-125mm f/3.5-5.6 dc. thanks for the links

I wouldn't fret about that much. The last time my dad bought a skinning knife, it took him about 3 months of bringing one home after another, honing the edges, checking the balance, curvature, proportion of back-edge, and I have no idea what else, before he found one which he deemed satisfactory. I think he had gone through about a dozen by then.

sounds like me