<p>I have a J2EE-based system which is running currently on Apache Tomcat. We are in discussions to move our production servers to the Glassfish server.</p>

<p>Can someone share their experiences with either of them?</p>

Here's
quite an old comparison
. As such, the capabilities of each server have doubtless improved.
Edit: Here is
a current comparison.
Both are more than stable enough for production use though. It's really going to come down to features.