I have a little poll Link about what the developer community want from a future debugger I had 62 people responding to the poll, Not a huge amount but anyway enough to see the direction. A future debugger of XPages needs SSJS debugging, java and client side debugging is not necessary.
It was a close run between new debugging features that I listed between conditional breakpoints and
backwards debugging and the backwards debugging won. It would be great to have both these functions in a future debugger. How could a backwards debugger work in Domino, well I think that it could work like this. When you start debugging every change to variables is logged the only variables that can be traced is your own variables. no objects. Then when you start to trace backwards these changes is shown in the debugger like playing a movie backwards.
Looking forward to the day when we get a debugger.