If you want one lens that can do most shots, I suggest the Nikon 18-200mm f/3.5-5.6 G ED-IF AF-S VR DX Zoom Nikkor
. This is what Treeroot shoots and it is one of the most versatile lenses ever made.
Canon probably has a similar lens if you want to stay in the Canon family.
This is a new, hot segment of the market: cameras that attempt to replicate the quality of an SLR without a mirror. I would take a look at the following:
The problem with these cameras is that they are still large. Honestly, if I was buying a non-DSLR camera, I would buy the Panasonic Lumix DMC-LX5
. This is essentially the same camera as the Leica D-LUX5
at half the price. I have the predecessor (LX3), and it's almost impossible to take a bad shot.