Broccoli is great simply blanched until bright green or roasted until charred and sweet, but I'm going to go out on a limb here and say that it's equally good when it's had the crap cooked out of it. Some time in the mid '90s, braised green vegetables seemed to go out of fashion, to the extent that it was nearly impossible to get a vegetable that wasn't cooked al dente in a restaurant. It became common practice for new cooks to undercook their vegetables. Heck, I've even heard some chefs that want their bean cooked al dente, ferchrissakes.
Thankfully, cooked vegetables seemed to come back in vogue right around the same time that chefs stopped calling their mayonnaise aioli and the world is a better place for it.
I first had pasta with slow-cooked broccoli at Jamie Bissonette and Ken Oringer's Coppa in Boston's South End and was blown away by its intense flavor. When cooked down in a rich tomato sauce, broccoli takes on an entirely different character with a deep, mildly sulfurous aroma that borders on meaty in its savoriness.
The key is to make sure your sauce is plenty acidic. This helps the pectin in the broccoli hold its cells together a bit tighter. Rather than reducing to mush, the broccoli develops flavor while still staying intact. Canned tomatoes are acidic on their own, but a glug of white wine adds both acid and flavor to the mix.
Of course, plenty of garlic and good olive oil are essential.