Ask HN: experience with outsourcing human resources

I'm about to hire a first employee, and I would prefer to hand a lot of the administrative burden over to someone else. I've investigated a few firms that handle payroll, but there are others that offer to handle everything that a company would normally hire human resources professionals to do. I have a basic understanding of payroll, health insurance, and 401k after running an single employee S-Corp for over a year, but I'm concerned about the legal complexities of having employees who aren't me. Does anybody here have experience with doing this? In particular, I've come across the concept of Professional Employer Organizations (AKA employee leasing firms) and the whole thing seems a bit fishy, especially since most of the information that's readily available seems to be produced by these firms themselves and I'm wondering what the practical difference is between this approach and (to use a term that seems to have been coined by the PEO industry) an Administrative Services Organization that handles the paperwork and provides advice but isn't the employer of record.