The answer to the question in the title depends on the definition of professional. I make my living from photography and I use it, so the answer is yes. But in the way that the photographic internet defines a professional photographer the answer is probably no. So why this contradiction?
For what I do it's almost perfect.
- The camera and lenses are pretty much the perfect size for me. Not too small and not too big and heavy.
- My stock photography involves a lot of walking, getting to and from locations and within the locations themselves and the system doesn't weigh me down.
- I'm also often in tourist areas and in the summer particularly there can be a lot of people around. So a relatively discrete camera is less liable to be 'misunderstood.' And apart from when I use the 55-135mm, that's the case.
- It's also a 'modular' system. I can change it from something that looks like a big smartphone when I use the screen in compact camera (and therefore relatively anonymous) mode, with the 23mm, to something more 'impressive.'
- The telephoto zoom adds some 'gravitas' should I require that.
- The camera is not silent but relatively quiet, the pared down menu and touchscreen means it's easy to set up and if I need to change anything the thumbwheels can alter the settings without me changing my hand position.
- The EVF is sharp and clear and the large rear screen works very well in bright sunlight.
- Files are sharp, because of the lack of an AA filter. There is no heavy-handed noise reduction embedded in the files.
- High(er) ISO performance is not the best, but pretty good nonetheless.
- The .DNG raw files can be processed quickly and seamlessly in Photoshop.
- The lenses, whilst not 'fast' have the quality I want and I'm more interested in stopping down for maximum depth of field rather than using them wide open.
- For me the system handles beautifully.
- Hand held video is surprisingly good with software stabilisation.
- Files have a nice depth of colour that is very useful for what I shoot.
- I can use manually focused 3rd. party lenses via an adapter.
- Battery life is reasonable.
- The OOC jpgs, are decent and can be used for reproduction.
- GPS tracking in the viewfinder. A lot of my libraries include location map info. This does it automatically.
But for many other professional photographers there would be some concerns.
- AF is not particularly fast and occasionally has difficulty 'locking on.'
- The 4 lenses currently available are far from what a multi tasking jobbing pro would require.
- The unconventional looks might raise some eyebrows for some jobs. A 'confused' client is generally not a happy client.
- Many would find the almost 100% touch screen control not what they are used to and liable to create problems because of unfamiliarity.
- Many professionals don't see Leicas (of any description) as serious working cameras. While appreciating the brands reputation, they are much more comfortable with Nikons and Canons.
- While the video offer is better than might be imagined, it falls somewhat short of what a photographer who shoots video would require.
- Despite being able to be upsized quite dramatically, 16MP file production is less than many would think of as being suitable for professional work.
- In terms of long term robustness and reliability the system is still very much in the newcomer category. How well it copes with long term use can only be assessed over time.
- The Wi_Fi remote app. is poor and keeps disconnecting.
Now I don't think that Leica themselves loose any sleep over whether a camera has a professional designation or not. They have always been much more associated with the social documentary side of photography. The film cameras certainly had (have - they still make them) a reputation for being rugged enough to operate in war zones and other 'inhospitable' situations certainly and there is no reason to assume that despite it's sublime good looks the Leica T is any different. The lenses are obviously seriously well put together, so I would doubt there would be any issues there. Plus not all professionals work in a way that leads to the eventual destruction of their cameras.
From what I've seen Leica are concerned about image quality first and foremost. Sure, it hasn't escaped their attention that many of their products carry a 'luxury brand' tag. But while many buy them because of that cachet reputation, most are aware of the history of the company and the fact the the Leica brand name is synonymous with quality throughout the design, manufacturing and operational process. I'm now on my ninth Leica body (2 M8's, an M9, X-Vario, X1 and X2 and a couple of rebadged Panasonics, D-Lux 4 and Digilux 3 as well as the T) and I've never had an issue with build quality. But professionals tend to stick with what they know and has tried and tested over the years.
Ultimately I think it's actually difficult to think of what kind of photographer the Leica T (Typ 701) might be suitable for. Because of the innovation and the radically different design and operation, it's pretty much writing it's own rule book. Whether this is good or bad and whether picking up design accolades and awards translates into sales and the beginning of a viable long term system that sells well is anyone's guess. I guess Leica know, but they don't share those sales figures with me.
In the meantime I'll continue to use and enjoy the system. Mathieu at Mirrorlessons is currently working with the system which should be interesting, so you'll get another opinion of working with the camera and lenses in due course, which will make a change, since there is very little long term use being documented on the photographic internet. It is a new system and will take a period of time before we have an idea of the long term prospects. I may be convinced already but it will need a lot of others to feel the same before we can make a genuine assessment of it's 'professional viability.' I'm doing my bit though and relishing it. It has become my favourite ever camera and picture taking system and since I've owned quite a few for me that counts for a lot.