Most people are not very receptive, but that's because it's a phone call interrupting their day, not because it's about Ron Paul. I've called 50 numbers and no one has been that receptive, but that's ok. What we're looking for here is a) convincing a few people to go the straw poll who wouldn't otherwise--and calling 2million people is worth it if we can get a few hundred this way as the impact is enormous and the cost, while tedious, is low, and b) to up name recognition for the caucuses. I try to say "if you can't make it to Ames be sure to consider Congressman Paul is the caucuses next year," and they're, of course, more receptive to that message as it's lower cost for them.
I've left a lot of messages, too, which might even be the best of all (other than finding immediate converts who want to know more from you) because it's less intrusive on their day and lets them find out about Ron Paul at their own pace.