Every now and then I'll see someone who says they get a sale from twitter. But when you add up the number of hours people spend there, I cannot imagine it is even worth one sale.
It's social, it's silly and my opinion seems to be in the minority. When I had a twitter account almost all of my followers were etsy sellers. Not my customers.
I know some people like it for the chatting, I felt stupid using it. I didn't feel like anything meaningful was said in 140 characters.
But most of all, it took away time from actually creating, interacting with real customers and better marketing.
If you find it useful for your business, then by all means, pursue it. But, you can run quite a successful business with out it. I have an etsy shop, a website and wholeslae accounts. I've worked very hard to get them all, and I do not use twitter.