My style of entertaining is very casual and easygoing (read more about my entertaining philosophy here!). I like my guests to feel comfortable and the atmosphere (dare I say ambiance?) is an important part of doing just that.
If we're hosting friends for dinner on a Saturday night, a formal florist-type bouquet isn't appropriate - it would say all of the wrong things about what I want the night to be.
My favorite method is to use several stems of the same type (or color) of flower. As a caterer and event planner, I knew that I could rely on these types of arrangements to always look great. They are hard to mess up!