I just published a new Java framework to use ISO8583 without too much hassle. It's called j8583 and it's available at SourceForge. It's LGPL so you can use it in commercial applications but any modifications done to the framework itself must be integrated into the library.
The main idea is to be able to easily create ISO8583 messages to send them over a socket and also to parse incoming ISO8583 messages without having to implement any parsing code. All the value types are implemented and can be parsed from the bitmap, you just have to tell the framework how many bytes the length header has and also how long is the ISO header if one is being used; the message factory returns an ISO8583 Message with all its values set. There are templates to create new messages with preset values in some fields, and also the message factory can use an external object to generate the trace numbers (from a DB sequence or whatever) and can set the date on new messages automatically.
If anyone finds it useful I would like to hear your comments.