All this talk about whether democracy in Egypt will be a good thing or a bad thing just goes to show how misunderstood the word democracy is. Democracy refers not so much to elections but to liberalism in the general sense of the word.
If Egyptians elect the Muslim Brotherhood in a free and fair election, and the Muslim Brotherhood then rigs or even cancels every election that follows, Egypt will not be in any way shape or form a democracy. It will be a dictatorship that happened to have an election.
Mature liberal democracies have checks and balances, the separation of powers, equal rights for minorities, restrictions on the power and reach of the victors, and guarantees that those who lose will not be persecuted.