When the Democrats debated last week, nothing happened. I think that's largely because there is little ideological difference between the candidates: all they can really do is disagree on how to achieve the goals they all value.
Not so with the Republicans. When 10 GOP candidates get together tonight in Los Angeles, there will be some who support abortion (Giuliani) and some who are violently against it (Brownback). There will some who hate illegal immigration in their bones (Tancredo) and some who have a kindlier position on the issue (McCain, Giuliani). There will be true conservatives (Huckabee, Brownback, others), some mushy conservatives (Romney, McCain, Giuliani), and one libertarian (Paul). I think the frontrunners will play it safe, but the rest of the pack might take a few nasty stabs in order to distinguish themselves.
Should make for good times. You can find a full lineup and a list of things to watch for at the New York Times' political blog, The Caucus.