Here's a slashdot article on buying a digital single lens reflex camera. Here are my comments on their main points. Granted, they suggest that a DSLR is not for everyone.
My experience is based on my Olympus D-40. (Not a DSLR).
Also note that I write this as a former SLR user for more than 25 years. I loved my Olympus OM-1 and miss it in many ways. (I still have it, I just don' t use it any more). Still, I think the digital medium has advantages that don't require going back to the old SLR format. I
Creative Control
My camera has all the controls mentioned, aperture, shutter speed, in camera sharpening, white balance, flash sync. I'm not sure it has a contrast setting. These all require using menus so I bet a DSLR may make some of these easier, but I can do them.
Superior Sensors
I'm not sure that I buy that a larger sensor (CCD?) is necessarily better. It will inherently have more pixels, but I definitely have enough pixels already with my 3.8 Mpx. My smaller sensor means my lens and camera can be smaller. Larger might be better but I'm not convinced.
Less Noise
I'm not convinced of this one either. I would need to see an objective spec on what the noise actually is. I have not experienced noise as a problem except in very low light situations. My camera does have a low noise setting.
Accessories
I concede this point. I really wish my camera at least had a way to attach and/orat least synchronize a flash. (I know you can sync with a slave of some type). I don't really feel the need to have lenses outside my zoom range (which is roughly equivalent to 35mm camera 35mm–100mm). A longer zoom range on a camera would be nice.
No shutter lag
This is huge and my greatest complaint about my camera. Newer, non DSLR cameras solve this problem though. A lot of it, I believe, has to do with the time it takes to unload the CCD and write to the memory device. So I don't think this is an advantage exclusive to DSLRs, but just to newer cameras.
Instant Startup
Maybe. This isn't that important to me. My camera starts up in three our four seconds. That's probably equivalent to taking a D/SLR out of a bag and removing the lens cap. (My camera fits in my pocket).
Higher Build Quality
Maybe. My camera does have a lot of plastic. It probably wouldn't withstand some abuse a more professional camera would. Still, it's pretty sturdy.
Viewfinder
My viewfinder zooms to match the lens. I grant that it's not perfect. The LCD provides a perfect match and I think the LCD is very useful as a viewfinder (though I typically don't use it unless I need to). An D/SLR viewfinder is a beautiful thing, but mine works pretty well.
Ergonomics
You need to learn my technique for holding a small digital camera. Thumbs up with your left hand. This creates a very stable platform with your left hand to support the camera. It also keeps your fingers from blocking the lens. Control the shutter, etc., with your right hand.
Price
No way. DSLRs are cheaper that DSLRs used to be, but always more expensive than the other digital cameras.