Our current system is prefolds, trifolded into "
insert socks", in a Flip or Bummis SuperLite cover. The insert socks aren't strictly necessary, but keep the prefold in place while trying to change a baby who is trying to crawl away.
We had to buy new covers recently to replace some worn-out hand-me-downs, and I wanted to love Thirsties, since everyone else does- but, we've tried three of their covers, and, for every one, the rise snaps would not stay closed. I was so disappointed, since everyone else loves them so much.