I like a lattice crust on a cherry pie, personally. That's my preferred way to eat it. I also don't like it to be too sweet -- or any fruit pie too sweet, for that matter. I want to be able to taste the fruit and not just sugar.
Cherries can be tart or very sweet, depending on the variety, so care should be taken when sweetening them. Usually, a third of a cup of sugar is sufficient for a pound of sliced cherries, unless they're very tart. Add sugar by the tablespoon and stop when they're more sweet than tart -- but still have a little tartness remaining.