I didn't buy a glider. I have a three week old and I have a rocker, and frankly I've never used that either. Perhaps I will when he's older.
I find it just as easy to sway the kid in my arms, or bounce him, or swing him around on my legs.
ETA: I just remembered that I thought about buying a glider, but it turns out that I'm so inflexible that it actually hurts to be in a glider. When it moves forward, it creates too much pressure on my super-tight hamstrings.