In my job I have investigated a number of Domino server crashes. In the majority of them where the crash has originated from code within an application (as opposed to 3rd party .dll based crashes) the fault has lain with the Java code.
The problem stems from the Java versions. Something you seem to have come across in the past as well.
Personally I would say that if you need to interact with applications outside Domino (manipulating graphics, communication to other websites/servers, etc.) then use Java otherwise stick with LotusScript. You can still have object oriented structure without the risk of servers crashing around your ears.