Start with the sensor, the Foveon 14 megapixel gives you color fidelity that other digital cameras can't touch. It's great to have this in such a small package. The camera is extremely compact and while you might think the 16.6mm fixed focus lens (28mm equiv. on 35mm camera) is limiting, it is perfect for urban street shooting. The lens quality is very good and the test shots I've taken so far look very promising.
Things I'd like to see; a larger buffer so you can keep shooting longer, a dedicated button on the rear of the camera for faster ISO changes, higher ISO up to 3200 even with all the noise, faster autofocus (though real street shooters always use manual prefocus anyway), a better grip, zero shutter lag -- an issue all digital cameras have and finally support in Lightroom and Photoshop RAW, which I would expect within the next three months or so.