Sure, you shall shoot with flash! With all the sharp and contrast rich lenses available for, say, the M-system, it is a shame not to use flashes. - For that is the point; use several flashes. Not just one mounted on the camera which gives this very ugly, flat and amateurish look.
I use a minimum of 2 flashes, but usually three. With my Canon 1Ds II I use three 550EX and a transmitter on the camera. Or one flash on the camera and 2 mounted on these foot that comes with it. This flash foot is a smart thing.
It is fun to experiment with how the flash is placed around the subject. But I have learned that the best result I get with two or more flashes reflected towards a white ceiling with the light thrown at an angle towards the camera.
See the two examples below of this classical Norwegian family lunch: The first picture is with existing light.
The 2. picture is with three flashes. Yes, I have left two of them in the picture so you can see where I have placed them:
1) a Vivitar 283 mounted on the M8 reflector pointing towards the ceiling. This is the flash that triggers the others.
2) another Vivitar 283 (you get them cheap these days) placed on a flash foot on top of the fridge. Note that it is pointed so that the light rays are pointing towards the camera.
3) a Canon 550EX (yes, it is possible to use them with Leica cameras, but only in manual mode and you have to set the output manually). Set at 100% power, pointint at the ceiling and also this pointed somewhat towards the camera.
Note that the light angles from the flashes on top of the fridge creates a more 3.dimensional effect on, say, the items on the table - like the Norewegian goat cheese.
I have also included a 3. picture. Also taken with these 3 flashes. I have left one of them in the picture (otherwise I would crop them away). This time one of them is standing on top of the piano to the right, so there is two pointing to the ceiling so that the light rays falls 'towards the camera'. Note also that the flash that you can see in the picture also lights up some of the background. - Which is another way of using several flashes, you can direct light towards an otherwise dark backgound.