Has anyone used Ideal In-Sure Push-In Wire Connectors? What is your opinion of them?

Depends on the application that I would use them. I can be a bit old fashioned, but have seen enough to know what will and will not work.

If your doing a bunch of ballast changes , or just want to use them to splice fixture wires, then fine, they will work.

If you want to use them for connecting building wires, splicing between lighting, outlets, something with substantial load on the wires, then these are not for me.

I will continue to twist my wires, and use the Ideal twist on wire nut.

My educated opinion.