It is like a digital SLR camera but tiny. You'we got the same big 24x16mm sensor that catches a lot of light and can create photos with a short depth-of-field. And you'we got the interchangeable lenses. But you don't have the bulk.
My first SLR was a Nikon F90 (N90 for those of you who haven't gone metric yet) and I'we bought a fair amount of lenses and stuff over the years. I was about to upgrade my Nikon DSLR - an aging D70s - when I realized most of my stuff was outdated. I have always felt locked in by my original choice and now I had a great opportunity to switch.
After some research I came to the conclusion that a mirrorless camera with interchangeable lenses made sens. And since I wanted the biggest sensor size possible, the brand new Sony NEX-5N looked like the best option.
It does everything a big, black DSLR does - except draw attention. But it does fit in the pocket of your jacket. It's great.
But I do kind of miss the "attention" part.