As a web developer who works with Web Services that are within the same solution as my front-end code most of the time, I found the ability to "attach" to a process to be a HUGE time saver.
Before I found this hidden gem, I would always have to set a breakpoint on some front-end code that called a web service method and step into it. Now that I know about this trick/feature I can easily set breakpoints on any part of my code that I want to which saves me loads of time and effort.