I love flipcharts. I use them to teach songs in primary, and for my children in Family Home Evening. Some of the charts have all of the lyrics, others key phrases, and others key words. Of course, we don't use them all of the time, and we memorize as much and as fast as possible.
I love use flipcharts when we haven't sung a song in awhile, and we may not have all of the words memorized anymore. There are so many wonderful primary songs out there, and we sometimes get into a rut and sing the same ones over and over. Flipcharts can help remedy that. Just think of them as a full-color hymnbook for children!