I have done a lot of city shooting with my Leica D Lux 3. It has an effective 28-100 zoom lens on it. That would be the same as about a 17-70. I've also shot with a 10-17 fisheye, but that is a whole different animal, and used a 12-24 on my Nikon D70. I also shoot almost every day with my 16-45.
I've found that while traveling and shooting in the city, 28-100 effective on the p&s works pretty well. But another factor there is that p&s cameras have much greater DOF than a dslr. So you have to take that into account. With the 16-45, I don't find myself at 16 very much but when I am, I'm there and probably wish I had it was a little shorter (heh, that's what she said). But in the city I'll be at 45 a lot more than 16. There is no way a 10-20 or 12-24 could be my walkaround lens in the city. ymmv. Also, I tend to do more towards the art side of things as opposed to documentation so you have to account for taste as well (examples here:
hk08 - Page 1).
The only time I used my 12-24 was when I had tough interior shots, and I was almost always down at 12-14mm so I could get coverage. As for landscapes, I've found the 16 will usually do the trick. No always, but usually. Enough so that I don't really want to haul another lens around unless I have something special I want to shoot.
Not to complicate matters, but you might also ponder the Ricoh GX-100. For the price of a decent zoom lens you get a pretty amazing p&s that a fair number of "serious" shooters use. It covers 24-70 effective, shoots raw, and is small. Small sensor cameras "draw"differently though, and you won't get the resolution that you will with the K100d. Different tool, but for city shooting, quite good.