Wow, it took me forever to remember what my password was...
In Java profiling hell right now... my compiler pass (that theoretically takes linear time) was identified as being 5 times slower than a similar (actually much more ambitious, though not necessarily linear) pass that my officemate hacked up.
I've managed to get the time down by a factor of 2 or so since then by playing with the order of basicblock traversals in the data-flow analyses but am not sure where the remaining hotspots are...
Continually frustrated by several aspects of Java language and libraries, but mostly by the lack of parameterized types. A student in the my group for 6.035 (Compiler Engineering) once told me that he had never seen any useful feature of parameterized types; am now convinced that anyone who would say such a thing has never coded a compiler (or perhaps any largish system?) before (I certainly know that he wasn't doing the coding for our system).
Can't wait for GJ to get integrated into Java3 or whatever.