There are many types of "professional" photographer and the kit that they choose to use depends on how they make their living. Gianni Galassi is a fine art photographer and can basically use whatever he wants.
I wrote a piece on my blog about this, citing the examples of Donovan Wylie and Alex Majoli who are both photo journalists who use compact cameras for their work.
There is also the example of magnum photographers who used Leica cameras in the days when 35mm was not regarded as professional.
Gianni on his website says:-
"I know, many pro have their customers attend their shootings, and they need to "wear" a big and expensive camera to impress them and prevent them from thinking that taking a good photograph is an easy task. And I'm aware that too many photographers have already had their customers stolen by the current point-and-shoot camera technology (which is, on the other hand, really outstanding!)."
There is unfortunately a perception that "Big Camera = Good Photographer" and though we all know that is a false impression, for someone making a living with their camera, perception can be everything. I walked in to a factory on a commission a while ago & pulled out a D3 + 70-200 F/2.8. Everybody took one step backwards and immediately assumed I knew what I was doing. They had no evidence to know what kind of photographer I was, but the gear I used seemed to indicate to them that I was to be taken seriously.
A good deal of my income is generated by stock and library photography & I can use whatever cameras I like for that. Consequently I use m4/3 much of the time. I have no problems with quality & I love the size, weight & unobtrusive nature of the cameras.
For commissioned work I have started taking along m4/3 cameras in addition to a Canon 5D Mk II outfit. My company is already shooting video on two GH1's and clients don't have any problem with that. Whether they would accept us turning up with a GF1 or an E-P1 for stills photography is another matter. However since we can "establish our credentials" with the Canon, whatever we use after that is basically left to us.
I know of a event portrait photography who "hides" a m4/3 camera inside an old plate camera. He disappears under the cloth takes the picture and re-emerges. No-one has ever complained about the quality of his work.
On the jpg issue, it depends entirely on the camera. Many news, sports, event and wedding photographers use jpgs. Where speed is critical they are invaluable. The busier you are, the less time you have to process images. I did back to back weddings recently & shot everything on jpg. I just didn't have the time (or to be honest - the inclination!) to process 3000 images. I find that in certain situations, such as using high ISO's in low light situations the camera does a better job of noise reduction than I can shooting raw. This is certainly true of my Canon & m4/3 cameras.