From what I've read, this is basically the same hardware as the d-lux 4. Differences: different coating on the lens (same lens) different firmware a longer warranty (either 2 or 3 years for Leica - different reviews give different figures - vs 1 year for the LX3). the red Leica logo! Also I've seen it suggested that there are some external bits of rubber trim on the LX3 which are not present on the Leica. I think you also get Capture One software with the Leica, which is a high-end RAW processing package.
Yes, you often hear that it is, and it really is exactly the same as the Leica. All the internal software is exactly the same, to the point where all the menu screens are exactly identical. If you purchase this camera, I would highly recommend getting the aftermarket book on the Dlux-4 as a way to learn the LX-3's features. You will find that everything is the same. People claim that the lens is somehow different, but given that both cameras are built and assembled in Japan, one has reason to suspect that the lens is the same too
A great camera, but fairly complex. A person can just point and shoot of course, but knowing enough about it to make use of it's massive number of adjustments is really the way to get what you are paying for.