You (Probably) Don't Want an SLR
You probably don’t want to buy an SLR camera. What you should be buying is a pocketable high quality point-and-shoot camera.
Here’s why:
SLRs are big and bulky.
You can’t take it everywhere with you and so you’ll take pictures less often with an SLR than you would with a pocketable point-and-shoot. There are situations where you just can’t take an SLR, especially if you have kids or are travelling with other luggage, where you can take a pocketable point-and-shoot. Buy a high quality point-and-shoot and you’ll take pictures in more locations of more things.
SLRs are expensive.
The entry level SLR cameras start around $500 for a kit with a crap lens. If you’re really getting the most out of your SLR, you’ll want better glass (lenses), especially if you shoot low light, since most kit lenses are very very slow (f-stop wise). Good lenses cost good money, prepare to spend more on lenses than on your camera (also, buy used, lenses don’t get much better over time and 5 year old tech is pretty much the same as today’s tech except for the image stabilization).
But if you want to really shoot like a pro, don’t buy the entry level SLR, you should spend more and get an upper level consumer or low level pro model. That’ll set you back even more, expect to spend a grand for really good quality stuff.
Then, you’ll need a bag, cause you can’t risk damaging your expensive camera. And with that spare lens you bought, you now have more than one thing to carry, and it’s kind of big.
And now that you have a bag and a spare lens, you have to consciously pack it along (see point 1). You’re not going to want to take it with you everywhere you go (I’m not going to take pictures at the fancy dinner restaurant, right? I don’t need to take the SLR this evening). Now, you’re going to miss shots.
High-end point-and-shoots take really good pictures
Until you’re limited by the camera, which will require you to apply some photo taking skills (which most people don’t have and don’t care to develop), an SLR won’t allow you to take better photos than a high quality point-and-shoot. And the high end point-and-shoots have the same sensors and (sometimes) faster glass than the low end SLRs. Many point-and-shoots have full (or almost full) manual modes, do macro down to 1 inch focus, and can run > 1 minute exposures. Some even have hot-shoes for external flashes. Many now come with f2 or faster lenses (that’s really good!).
You can do a hell of a lot with a high quality point-and-shoot. And it’ll fit in your pocket. So, you’ll take it to that fancy restaurant, and you’ll take pictures there, too.
The best camera for the job is the one you have with you!
The iPhone has a good camera, for a phone. But, even $200 point-and-shoots will put it to shame.
So, if you’re out, and you don’t have your SLR, use your iPhone. But the low light performance will suck, and you probably won’t be able to get good 8x10 inch prints without noticeable grain.
If you had your pocketable point-and-shoot, you’d get good pictures.
Conclusion
It really all comes down to money and taking more pictures. Taking more pictures, or having the opportunity to, means having a camera with you more often.
Buy the $350 point-and-shoot. Put it in your pocket when you go places. Take pictures. Job done.
Or, spend > $1k on an SLR, buy a bag, and lug it around. I hear those fanny pack bags are nice…
Want to read more about the Canon S100 point-and-shoot I like? dpreview has good things to say.
Addendum
Of course, if you’re a photo journalist, taking a photography course, or are really into one or two specific types of photography (landscapes, night shots, wildlife, sports, etc) an SLR probably is the right camera. But if you’re doing these things, you probably already own a nice camera, a bunch of lenses, and you’re heavily invested in going on trips with your SLR for the main purpose of taking the pictures you like to take.
Most people aren’t like this.
I used to be (back when film was cool and Kodak made profits), but now I just want to take pictures and not think about it… So do 95% of people out there. And for those people (and quite a few of the “already own an SLR” people), a really nice piont-and-shoot will get the job done.