Message brokering across different systems, with transactionality and the ability to have fine tuned control over what happens using Java (or other languages), instead of a heavy, proprietary languages. One situation that it doesn't fit very well (as far as I have experienced) is when your workflow requires significant data mapping. While possible when using Java tooling, some other visual data mapping tools in other integration frameworks are easier to work with.
If the environment has many different protocols for data exchange between partners and most of the protocols follow some standards like EDI X12, TIBCO BusinessConnect should be a good tool to take care this business use case. If the environment has a few simple protocols for data exchange, e.g. SFTP, FTPS or emails, some lighter weight tools will be enough and TIBCO BusinessConnect may be an overkill tool.
Camel has an easy learning curve. It is fairly well documented and there are about 5-6 books on Camel.
There is a large user group and blogs devoted to all things Camel and the developers of Camel provide quick answers and have also been very quick to patch Camel, when bugs are reported.
Camel integrates well with well known frameworks like Spring, and other middleware products like Apache Karaf and Servicemix.
There are over 150 components for the Camel framework that help integrate with diverse software platforms.
When a new version is released, its better to test it thoroughly before letting customers apply the release in their real time environment. There were missing functionalities from the previous versions which were not identified ahead of time.
If you are looking for a Java-based open source low cost equivalent to webMethods or Azure Logic Apps, Apache Camel is an excellent choice as it is mature and widely deployed, and included in many vendored Java application servers too such as Redhat JBoss EAP. Apache Camel is lacking on the GUI tooling side compared to commercial products such as webMethods or Azure Logic Apps.
The main reason TIBCO BusinessConnect was selected is because of the overall solution it provides with the different TIBCO products. Since TIBCO BusinessWorks and TIBCO Enterprise Message Service are already in place and the canonical model is already built and integrated into the Information Bus, TIBCO BusinessConnect is the best tool to work with them.
Very fast time to market in that so many components are available to use immediately.
Error handling mechanisms and patterns of practice are robust and easy to use which in turn has made our application more robust from the start, so fewer bugs.
However, testing and debugging routes is more challenging than working is standard Java so that takes more time (less time than writing the components from scratch).
Most people don't know Camel coming in and many junior developers find it overwhelming and are not enthusiastic to learn it. So finding people that want to develop/maintain it is a challenge.