I've had several.
The key feature is that they bring something to the table: I don't actually need technical guidance on how to build the product -- I (or another engineer) knows enough to solve the technical aspects, that's why the corporation is paying me (or them). But what I do need is help coordinating with other teams, help interacting with executives, help prioritizing tasks, help with the kinds of brainstorming exercises that nucleate the project plan, help with understanding and interpreting customer feedback, etc. Colloquially, the "people side" of the job -- it's just not what my skill set is.
So, I actually prefer non-technical PMs: I want people who complement me, not people who are probably less informed about technical issues trying to micromanage my choices there. A non-technical PM is bring a skill set that diversifies a team of engineers, and helps the team more successfully do its job of interacting with both the corporation and customers.
If the PMs here will indulge a couple questions from me:
1. What skills are most useful in an engineer, and how do we make you look good/help you make us look good?
2. What advice would you give to an engineer looking to move into a role like technical adviser, which more directly interfaces with management and executives?