users@glassfish had a discussion on what are the key differentiators of GlassFish. This blog summarizes them. Here is a list of distinguishing features:

1. Fastest open source application server (883.66, highly scalable).
2. Centralized management of clusters and instances distributed across multiple servers.
3. Microsoft .NET 3.0 interoperability
4. Java Business Integration and Open ESB
5. Call flow analysis for diagnosing performance problems
6. High performing  message queue implementation (Open Message Queue), with a highly available message store.
7. SIP Servlet support and Telco Support via SailFin
8. Very small footprint and flexibility via modularity in GlassFish v3.

And here is a list that makes the technical features all the more appealing:

1. Out-of-the-box experience - Download to "sample app" in 10 minute
2. Impressive monthly downloads - 430k for December 2007
3. Good support on the forums.
4. Update Center for downloading additional features, samples, blueprints, etc.
5. Outstanding documentation
6. Number of releases - Released GlassFish v1 in May 06, GlassFish v1 UR1, GlassFish v2 and GFv2 UR1. Now working on GlassFish v2.1 and GlassFish v3.
7. Domain structure is nice, easy to upgrade the server and keep your configs in place.
8. Packaging is nice and compact and does not expose underlying architecture. Specifically, you don't have to be an expert on Glassfish and how its built or designed to get good value out of it. The others are certainly powerful and flexible architectures, but they expose that complexity to you as a user, and it affects the learning curve.
9. Gradual complexity. The admin gui, command line gui, the config files, the documentation make the simple stuff simple and the difficult stuff possible. Combined with Java EE 5, things mostly just work. Yet you have the depth of all of the configurations options to be able to take it where you want to go.

What is your favorite feature ?

Technorati: glassfish appserver performance