I have taken some night shots to compare the noise level of these three cameras that I own: Sony Alpha NEX-5N, Canon T1i and Panasonic Lumix GF2. The Sony and Panasonic cameras are both mirrorless interchangeable lens cameras, the Canon is a DSLR. In terms of price point when introduced to market with a kit lens, the Canon is the most expensive of the three, the Panasonic is the cheapest.
All these cameras have different sensor sensitivity. The most limiting of them is the Panasonic Lumix GF2 with a highest ISO 6400. The Canon T1i has the highest ISO at 12800 and Sony Alpha NEX-5N has the highest ISO at 25600. The above pictures are 100% crop at ISO 6400 for a fair comparison. The Sony Alpha NEX-5N compares very favourably to the Canon T1i, if not better. The Alpha NEX-5N, having the APS-C size sensor (same size as the DSLR) seems to have given it a big image quality advantage over the Lumix GF2.