There's a value vs. cost equation that only you can answer. Will the time and effort you put into blogging be returned in business gained? Can the time you spend on blogging be better spent elsewhere? How can you measure success with blogging?
Cost: time, stress, and money. Value: demonstrates expertise, raises search engine visibility, generates leads, leads the media to your door.
I really think blogging is a great way to stay in touch with people who are interested in your winery, but it takes effort, and probably appeals most to people who are closet writers to begin with. If only that pesky wine would sell itself!
John Jantsch is more succinct: Blog, dammit!
While you're at it, check out Rich's post on Your 2008 Web Marketing Plan.