A DSLR is not the ideal camera for street photography. Can it be done? Sure! But it is just too big and bulky and does not allow a photographer to be discreet. No wonder then that the Leica is still the king of street photography...Actually, I would like to get a Leica for this reason. I was talking to a guy with Leica M9 who told me that his kids, who shoot Canon DSLRs with large glass, get barraged by tourists to take their shots while he goes unnoticed with the Leica. He let me play with the camera and it feels good in the hand.
The problem with the M9 is: cost, poor high ISO performance, and lack of lenses :-). When I say lack of lenses, I do not mean that there are no good lenses - the Leica M lenses are the best in their focal length range, but not easily available. Since all of this is hand built, one often waits for a long time for a lens to become available and on eBay, competition can be fierce!
I am hoping that the M10 (rumored: Photokina 2012) will have much better high ISO performance (possibly Sony CMOS sensor) and their mirror-less solution with an APS-C sensor and using R series lenses at a lower price point will make these cameras available to all street photographers.
But, there is always the Sony NEX-7, Olympus PEN and Fuji X-Pro 1 to look at for street photography - just need really good lenses for them...
Or a 7D!