Well, I was looking into how to install and use NetBeans (NetBeans, unlike Eclipse, does not ship with Fedora), and hadn't gotten much of anywhere until I had a lot of time (on a flight), and was left with seeng whether I could get anywhere with the tools which I have already installed. That means gcj and gprof. I got gprof working fine on a short test program (where it correctly identified the bottleneck), but didn't (yet) succeed in running it on mayfly.
I suppose if people would find them helpful, I could upload my test programs and build scripts, but basically they boiled down to:
gcj --main=Profilee -pg Profilee.java
Getting something like this invoked from ant is largely a boring but more or less straightforward matter (although it wasn't clear to me how the classpath relates to the class and java files specified on the command line). But at least one of my invocations led to a runaway linker which made my machine swap for quite a while before I finally gave up. So although it is premature to declare victory on this just yet, I did want to report on my success with the test program.