Currently concentrating on Micro Four Thirds cameras (M43)
Back in the good old days I was a 35mm (full frame) Canon SLR film camera user, a member of the Bureau of Freelance photographers,had my own dark room, etc but eventually got fed up with carrying around a selection of large heavy lenses which ended up more often than not being left at home unless I was going on a specific photo shoot. I am currently using small Micro Four Thirds (MFT or M4/3) sensor mirrorless equipment so ultimate image quality won't theoretically be as high as the larger sensor cameras especially at higher ISO settings but the smaller size and lower weight of the camera and lenses makes it easier to carry around and therefore less likely to be left behind. In fact the Panasonic G9 actually has higher dynamic range than the Canon 5D MKIII full frame Pro camera at moderate ISO and the G9 can do many things I appreciate that the 5D3 is incapable of not to mention having the incredible 5 axis stabilisation built in (one of the best systems in the world).
Reading the various camera forums it is easy to think that only the best and latest systems with the biggest sensors will do but I think it is very easy to get carried away and lose perspective. In truth, for most people, almost any modern enthusiast level digital camera is capable of producing images of more than adequate resolution/quality even for large poster size prints let alone for on-line use for which they are actually over kill and will need to be reduced in size. I have a photo I took of a sheep 50 yards away with my Panasonic G80 camera (a generation before my current G9) using the small 14-140mm Zoom lens which came with my older G6 (which is a good lens but not regarded as being as high quality as my Leica lenses). When you zoom right into that photo down to pixel level you can actually read the serial number on the sheep's ear tag, detail you would never see even in a 10"x8" print, so how high a resolution do you really need?!
If you look at my flickr gallery even my old Panasonic G6, which technology wise is four generations older than my current G9 and can be picked up on ebay now for little more than £100, produced some nice looking images e.g. the Arisaig sunsets or the Fladda Island Lighthouse. In the real world, away from the camera forums, people look and just see a "nice" picture or an artistic image, they don't sit there enlarging a photo to 100% and pixel peeping. So don't be put off, get out there and take photos, even if it is only with a compact camera or your phone!
In addition if your camera is capable of saving photos in RAW format then read my article on using RAW format and how, with post processing, it can unleash the full capabilities of your camera sensor.