Having done photography for a fair number of years I am now treading on very dangerous territory. Giving opinion on which camera to buy. It's a question a lot of budding photographers and casual photographers ask me all the time. The problem is there is no one single answer for all of them. Each one has a different need and a different suggestion is required.
On a personal front I shoot Nikon though I have shot with a Cannon and Sony as well. I used to shoot with a film range finder made by Yashica (which was awesome). For a brief period even shot with a Zenit film camera and a early generation point and shoot from Olympus. Having gone though so many brands and different types of camera's , I can say one thing with reasonable certainty, the brand of camera does not matter. ( I just killed any opportunity of being sponsored by any camera manufacturer!!!) [ Though I have not shot medium or large format so can't comment on that... perhaps a glimmer of hope]
In fact a lot of cameras in cell phones are really awesome you might not even want to purchase a camera. So the question arises why would you want to buy a camera. Now that I have compounded the problem let me provide a solution too. If you have been watching the advancements in technology when it comes to digital cameras, you would have noticed that the war stared by cramming mega pixels on the sensor to High ISO performance to frame rates so on and only the All Mighty knows where is going to end.
Now this a general advice and I am not responsible for any purchasing decision you make (standard disclaimer out of the way!!!!)
Mega pixel - For most average human being printing of digital images is an after thought. If you do want to print a small image or an album for that matter, a camera with 8-12 mega pixels is more than enough. If you want to want to get a print the size of a house or a bill board more mega pixels is required but for the average user 8-12 is enough.
ISO- This is bit of a though one. When I started out I used to shoot at higher ISO for a variety of reasons but on a personal front, I now mostly only shoot between ISO 100-320.[I wish my camera went to ISO 50 or 25 especially on sunny days] Rarely do I feel the need to go right up to the very high end of usable ISO. Though I do use Flash to compensate for lack of light but. High ISO performance is only important to you if you are shooting action or doing work professionally and have to deal with poor light, for instance, weddings, where you have less control over light. One thing to note, if there is very ISO performance on the camera usually ISO performance at lower ISO is also also good with lower colour noise. So a camera with High ISO of 6400 should have good noise reduction algorithms at ISO 800 or 1600 making the image usable
Point and shoot, Semi DSLR(AKA Mega zooms) Mirror less cameras or SLR: This is an interesting one.Over the years point and shoots have become really advanced. In fact a point and shoot today, in some ways, is more advanced than the pro camera body of 10 years ago!!! For some point and shoots the glass in the camera is better than the kit lens glass. If you are picking a point and shoot try and take one which opens up to an aperture of f2 or 2.8 this usually improves low light performance and also tend to be a bit more expensive. It is worth the additional expense. They also have higher flash sync speed compared to DSLR's . These ones would have full manual controls too giving you more creative options. [Cannon's G12 and Nikon's Coolpix P7100 comes to mind]
Mega zooms Mirror less or DSLR. I am not a big fan of Mega zooms. They have a lot of lens distortion and personally I found my self waking less or looking for better angels to photograph using mega zooms. There is a case for these but these are like Trishanku, neither here nor there .
Mirror-less cameras (with inter-changeable lenses) are fast catching up to DSLR's when it comes to performance in the dynamic range and even frames per second (FPS). Some Mirror less cameras out perform high end pro cameras for FPS because there is no mirror going up and down. It appears that this is the future and most DSLR's would eventually end up being mirror less. There used to be a complaint that the electronic view finder is not as quick as the optical view finder, which is still true in some cases but in the future the will be as fast as optical viewfinders [They will offer many more features like zooming in to the pixel level at the view finder level which would be awesome for macro shooters.] So if already have DSLR and don't need to replace it any time soon then defer your purchase a bit longer and you will get these features. They will have lenses corrected for that sensor and you will save a lot of money.
Last but not least, if you still cant decide based on features and settings and brand go to a camera store where all the brands of camera gear are there pick, it up in your hands and go with the one that makes you fell good while shooting. The camera is a tool, if the tool makes you happy you will most likely want to do amazing things with it and in all probability you will.
UPDATE : Here are a couple of links I found which should help you take a better decision on cameras. They are light years ahead that your's truly when it comes to knowledge on cameras. Both are really great.
Scott Bourne is an amazing photographer, with years of experience and he knows what he is talking about, check out his recommendation on What Camera Should I Buy? UPDATED VERSION – April 2012.
Trey Ratcliff gives insight into the future of camera, it's a must read if you can wait for a camera update, do check out his post on DSLRS ARE A DYING BREED – 3RD GEN CAMERAS ARE THE FUTURE