I've been using my Pentax Q (Q7, specifically) for over a year now. Any regular visitor to my blog has probably noticed that over time, the ratio of shots taken with my SLR and with the Q has been shifting further and further towards the Q.
The Q is a camera that makes most "serious" photographers laugh at it (without using one, of course). What a reputation to have. And I do almost see their point: when I first heard about the Q I also dismissed it as being likely incapable of taking decent pictures. And I bought myself a Pentax K-01, which was a complete disaster of a camera (sorry Pentax, but I think you also came to the same conclusion). Well, my decision to sell the K-01 to buy the Q was a very good decision.
There is almost no situation where the Q has been found lacking. And yes, again, I will readily admit that the Q7 has a very small sensor and the image quality is therefore pretty much by definition never going to match that of bigger sensor cameras.
But this is missing the point.
The Q can perform in pretty much any situation, and somehow encourages you to throw out the rulebook and get a bit creative. For instance, one of my favourite pastimes with the Q is to set it to shutter priority mode and set the shutter speed to 1/500 of a second, enclose it in my hand so it's almost invisible, and then wander around places with people while trying to snap candid portraits. Yes, my hit rate is obviously going to be very low indeed, but sometimes I get some very pleasing results.
For street photography in general, the Q is fantastic. With the tiny little 15-40mm f2.8 lens (equivalent to roughly 60-250mm), the camera still looks like a very small point and shoot camera, when in reality you can be zooming in on people from some distance away. Sitting at an event, the Q and 06 lens can be used to capture great portraits of people quite unobtrusively. Certainly better than a great big SLR and big zoom lens and thunking sound of the mirror.
The Q7 is also a whiz with infrared photography. Not all digital cameras are good with infrared, but the Q7 could almost have been designed for it: the sensor is sensitive enough to infrared light that it the image shows up very clearly on the live-view screen, and even allows perfect auto-focussing. So, stick the Q7 on a tripod, set it to manual mode and start capturing dreamlike infrared shots.
The Q is also, of course, an interchangeable lens camera. There are some great lenses designed for the camera (I particularly like the 01 8.5mm, 06 15-45mm and the quite unique Mount Shield). And also, you can mount lenses from other camera systems with an appropriate adapter. For instance, I have mounted my Sigma 50-500mm to turn the Q (with its large crop factor due to the small sensor) into a fairly impressive telescope for capturing shots of the moon. And, similarly, the Q with a macro lens can take shots that look like they were taken through a microscope as they are so close in and with such good detail (the benefit of its wide depth of field, though often assisted with a bit of focus stacking).
More than anything though, the Q encourages spontaneity (and filling up disk space..). The camera (and extra lenses and accessories) truly is able to be carried anywhere (the camera itself can be easily slipped into a jacket pocket). I didn't realise how good it would feel to shed the rather crushing weight of SLR and lenses in favour of the Q. Travel light and be free!
What I am trying to say is this: I feel that I am a reasonably decent photographer. And I feel that many of the shots I have taken with my Q have been among my best photographs, photographs that I would gladly print to a large size and hang on a wall.
Sometimes I do want the pure image quality, resolution, and dynamic range that my SLR provides. Other times, those things aren't paramount. At those times, I find myself reaching for the Q more and more often.
Photographs need to be interesting, creative, and tell some kind of story. The Q encourages this.
I'd encourage any photographer to give the Q a whirl, particularly those who find themselves in a rut and are taking the same kind of photos over and over: the Q might help them break free and find a new creative voice.
In summary, while I own a super Pentax SLR (the K3, which I feel will be a hard camera for Pentax to better), my favourite camera is the Q7.
With no further commentary on what they are or what lens/settings were used, here is a pretty wide variety of shots taken with the Q7: