What part of the synthetic oil allowing longer OCI's, cleaner engine, better cold-engine fuel economy, etc has anything to do with a 0w30 vs a 5w30. Synthetic come in 5w30, 10w30, 15w40, etc as much as any conventional. The OP didn't say anything about synthetics, just the winter rating. And I agree with him. I commonly use a 15w40 in cold with no problems. Even starting at -10F as a couple of nights ago in Minnesota. The engine that it is in has 337,000 miles on it and I have taken previous engines to 1.4 million without a major repair on a 15w40 conventional, running only the upper tier of the U.S., Ontario, and Quebec year round. Granted, I use synthetic blends now for a number of reasons as opposed to just a conventional as in the past, but a far cry from some 0w40 full synthetic deal, and I have no oil related problems.
The OP is spot on. A 5w30 will work just fine for what the majority of folks deal with for cold weather. And as the OP stated, those of us that have lived in nasty, serious cold like NWT or interior of Alaska, we used oil pan heaters, block heaters, battery warmers, etc, so oil flow was a non issue.