It all depends on how the application is written. Many C applications can be quite boggy slow when you make them do the same things that most java bogs down on: graphics, UTF-8, etc.
Look at how slow grep and some other Linux applications got when they started dealing with UTF-8 environments versus good old 'C' environment. Or how slow some applications could be when run in a 'newer' graphical terminal versus say a console or older xterm.
The biggest problem that people run into is that few development groups work on the hardware many users have (though I don't think I have any 200Mhz working systems here anymore myself).