Compared to business school in the post:
* I've got about 5 more years of school,
* school isn't costing me anything (I get a ~$20k/yr stipend; no tuition),
* I'm not enjoying myself at all (lots of hard core classes, required to pass preliminary tests in a limited number of sittings, boring city, boring people, boring school, no friends),
* the payoff is slim-to-none. I can't find evidence that a physics PhD is worth much in, say, software engineering. An MIT PhD student just told me he's heard ~$120k typical-ish starting salary in software engineering with a physics PhD (and he was trying to talk me into staying). That doesn't sound worth it at all! "Starting" salary!--if you don't count the 5-7 years of school (basically work).
I could go on, but I'm interested if anyone's got an opinion or some advice. It's a bit similar to the MBA decision.