I've used NikWax to do a really nice waterproofing job on an old 60/40 shell I have. (How many here are old enough to remember 60/40???) I was amazed at how well it worked. Water beaded right up on that 30+ year old shell. I tested it with a yard hose and nozzle. Stayed 99% dry after a good 10 second full force burst of water. Real life tests have been limited to light drizzle, but it came through that perfectly (as expected). I used the NikWax variety that you dump into the washing machine, not the spray-on kind.

In a massive hours long downpour I'd probably trust one of my newer waterproof-breathables to keep me dry, excepting sweat, but short of hurricane conditions I actually prefer the breathability and soft comfort of that old 60/40/NikWax thing. "Waterprrof-breathable" is a great marketing term and concept, yet to be achieved in reality. "More breathable than a trashbag" - yes, more breathable than 60/40/NikWax - no. All that being said, I typically take my new wiz-bang shell along rather than my old 60/40 on hikes if there's significant chance of heavy rain. It's smaller and lighter. I'm a hypocrit ... what can I say?!