I've been shooting digital since 1996. I have owned a variety of cameras that would take a paragraph to list and many thousands of dollars. I like the Canon line - the 10D, 20D or 30D are very nice and would be fine for what you're looking for. Don't be afraid to buy used - you'll save a ton of money buying last year's model. Many of my friends like the Nikon D70 and D100. The 10D, 20D and 30D have really low noise at higher ISO, which is why I'd recommend any of these.

I also have 3 point and shoot cameras in the house. For weddings or events, the point and shoots stay home unless I want to capture video clips.

One thing you'll gain on a DSLR is practically zero shutter lag. If you need to capture an expression, it's dumb luck if you can capture it with most point and shoot cameras.

If budget is an issue, get one of the cheaper Rebel DSLRs or Nikon D50\D70 and put your money into a good lens and external flash. If you get a body\lens package - the focal length is usually good, but the lens won't be fast enough as described in earlier posts.

Good lenses for Canon:
17-35 f/2.8, 16-35 f/2.8, 24-70 f/2.8, 50mm f/1.8. If you are free to move around, the 17-35 f/2.8 is a fine "press" lens. The 24-70 f/2.8 is nice, but it is heavy. The 70-200mm f/2.8 is also a nice lens if you want to get farther away from your subjects. The 50mm is so cheap, you should get that lens regardless.

From what I've found, image stabilized lenses do not work for this kind of work unless your subjects hold still. Everything around the podium will be sharp, and any movement from the subject will cause blur. If you're thinking Canon's 28-135mm IS lens will do the trick - forget it - it's a crappy lens for this kind of work. Don't forget, opening up the lens kills your depth of field, a higher ISO and flash help.

Best of luck.

Mark