I don't know if you've checked out the sample images of the 17-35 on pbase.com. Just in case you haven't, then here's the link:
Sigma 17-35mm f/2.8-4 EX DG ASP HSM Lens Sample Photos and Specifications
If you want to compare them with the kit lens, here's the link to the kit lens samples:
Pentax smc P-DA 18-55mm f/3.5-5.6 Lens Sample Photos and Specifications
I looked at getting this lens myself, but the IQ on the different shots seemed to be inconsistent (of course you have to consider photographer skill, as well). I've got the kit lens and will have the Sigma 17-70/2.8-4 by the end of the week. Here are some sample photos from this lens:
Sigma 17-70mm f/2.8-4.5 DC Macro Lens Sample Photos and Specifications
If you've got the extra money, I would say get the 17-70, as you can get them gently used for around $300.
For the money, the kit lens isn't bad at all and covers a wider range than the 17-35. If you decide to get the kit lens, it would actually be cheaper to get it separately rather than buy it with the body. If you go on the Marketplace or Fleabay, you'll find that you can pick up a gently used kit lens for around $50 or so, which is a lot cheaper than $110. What happens is a lot of people will buy the body/kit lens combo initially, but eventually upgrade to a better lens in this range. I haven't decided yet whether I'm going to hang on to my kit lens or get rid of it once I get my 17-70, though.
HTH,
Heather