I noticed that one of the perks of being a partner is “Migration Support. Get support migrating your client sites from other platforms to Wix.”
Has anyone taken advantage of this, and how did it work?
I’m not sure who here has utilized it, but it’s intended to assist partners who have clients on other platforms move to Wix. We work with you to help iron out any product technical challenges you may have. Most of the partners are very familiar with Wix so they do not utilize this, but those that are coming from other platforms will get a lot of value from it. Does that make sense? 
My methodology has typically been to build the infrastructure for a client’s new website and then engage in a lot of “copying/pasting” form their old site to the new.
Sounds like a solid plan - sometimes it’s tricky moving from, let’s say, a blog on one platform to Wix blog. Not everyone is aware of the blog migration tool.