Ask Engadget: Best digital SLR?

Ask Engadget

Alright, time for another Ask Engadget. Last week Dan wanted to know what stuff people kept on their USB keychain drives, this week reader Martha B. has a question about digital cameras:

I have a small digital camera which I love (the Pentax Optio S), but for taking nicer pictures I'm still using a regular SLR film camera. It's starting to show its age, so I've been thinking about taking the plunge and buying one of those new digital SLR cameras, and am at a loss about how to choose one. Are the cheaper ones like the Canon Digital Rebel good enough, or is it worth spending the money for a more professional camera? What else should I look for? If I buy a Nikon will I be able to use all the lenses from my old Nikon SLR?

Any advice?