Request for thoughts on open source consulting

I know many of the folks reading this list have done consulting of one form or another so I'd like to tap your collective wisdom with a few questions:

1. Is there much demand for consulting work on open source projects (including sponsored OSS development)? For example, somebody wants to integrate some open source into their product. Or they want a feature or bug fix for some Apache, Eclipse, Linux, JBoss, or MySQL component. They could just file a request for enhancement or bug fix and hope somebody would do it, but if it's important to them they could pay somebody to do it. How common is this?

2. How do clients feel about having the code they paid for becoming open source? Is this a hard sell?

3. What is the best/common practice for this? Would a join copyright between the client and consultant do the trick? That way the client could use the code however they want (including in proprietary systems) and the consultant could use the code in other projects and release it as open source.

Thanks for your input and advice,
--Ed