I was turned on to a delicious sweet vermouth, Dolin, by a very good mixologist girlfriend of mine, Lara Nixon, several months ago. She made me a Manhattan cocktail with Dolin sweet vermouth and I was changed forever. Friends, throw out your Cinzano, your Martini and Rossi, and get yourself over to your fancy liqour store for a bottle of Dolin sweet vermouth (while you're at it, get the dry one too--it is equally wonderful).
Here's the deal: when you've got a superior sweet vermouth on hand, change the ratio of your bourbon to vermouth to equal parts. Most Manhattans call for 2 parts bourbon and about one part vermouth, making a very strong cocktail (Maker's Mark, for instance, is 45% alcohol--most vodkas and gins are 40%). A high quality vermouth--usually about 16% alcohol--both enhances your drink and lowers the alcohol content. It's a win-win!
So friends, please revisit the Manhattan, and do it in this old-style classic way. And don't forget the bitters!