Vassili, you wrote:
Compact digital cameras with small 1/2.5" sensor usually has better depth-of-field because they have smaller focal length in absolute value. So f/3.5 on small cameras has better depth of field then f/3.5 on Digital SLR.
However this particular one has 1/1.72" sensor which is pretty good!
You are correct, and thank you for pointing this out. But, before everyone rushes out to buy a digital camera with a tiny CCD, it should be understood that as you decrease the CCD size, you are trading away image quality. One aspect to consider is correct perspective. A genuine macro lens not only allows one to focus more closely (it is measured from the focal plane, marked on the body, not from the front of the lens, to the object) or to use smaller apertures, but also have correct perspective. For wider-angle zoom lenses, as you zoom out, objects that are or have straight lines may appear bent or curved. With zoom lenses, one way to minimize or eliminate this distortion is to zoom in, meaning using a longer focal length. Ideally, if you have a digital SLR, use a genuine macro lens. I have two, and prefer the Nikkor 60mm Micro for its working shooting distances.
There are two trends today.
One is toward full-frame 35mm (24x36mm) CCDs, which is primarily driven by compatibility with 35mm cameras and lenses. 35mm represents a benchmark. Nikon is about to debut its first full-frame digital SLR, the D3 (its pricetag is $5K for the body alone, without memory card [it can hold two]). Canon has been selling such digital SLRs for a couple of years, perhaps more (I don't keep track of Canon's developments).
The other trend is toward smaller digital cameras. They are getting smaller, thinner, and lighter. And, as a benefit for us consumers, their image quality is also increasing. And, as you wrote, they benefit from greater depth-of-field. If I were to buy a more compact digital camera today, something more compact than a digital SLR, I would probably buy the Canon PowerShot G9. Soon, its capabilities will be found in cameras a fraction of its size.