Why Florida matters

It's unlikely it's delegates will actually matter. Assuming Clinton wins FL, the only way she would have enough votes to seat FL would be if she also already had enough votes to win. So their votes will only count if the contest has already been won.

However, there are two ways that FL can affect the dem race:

Expectations/Coverage
If Hillary beats or misses expectations drastically there will be some noise from the press, positive or neg respectively. Likewise if she succeeds in pushing the line that FL matters and the press follow her lead on it it could affect public opinion.

Republican Results
For tonight you can count Hillary in Romney's camp. Or rather, in the anti-McCain camp. If McCain wins he'll basically have the nomination wrapped up, with all the momentum going into Super Tuesday.

And a (presumptive) Republican nominee will immediately prompt head-to-head race comparisons. This is a weak point for Hillary, statistically the head-to-heads with McCain have her doing slightly worse than Obama. But, more importantly, in the general electorate Obama has been making huge gains in the electability question.

So don't be too surprised when Bill suggests Hillary and McCain are old friends... In Republican circles being friends with Hillary is considered slightly worse than shaking hands with the devil. As they say, with friends like these...