I've worked in restaurants, and for a time conducted internal audits (same criteria as external inspectors, plus additional criteria) for sister restaurants. I generally don't look at health inspection grades, figuring if they are open, it can't be that bad (and, frankly, given I eat some street food from highly dodgy locations, I can't be too precious!)
Every single friends' kitchen I can think of would fail a commercial inspection, but I still eat in their homes.
No separate hand washing sink in the kitchen area (sorry, bathrooms don't count), no thermometer in the fridge and freezer (mine is the only one I can think of that does), no separate colour chopping boards for raw meat, cooked meat, fish, dairy, veggies etc. (I do actually have meat and non meat boards, but quite happily cut cheese and tomatoes on the same one). I store eggs on the top shelf of my fridge (they have to be on the bottom in a restaurant), I don't date label everything I open (say, a jar of salsa or mayo) and simply rely on my own recollection as to how old it might be. I have glasses in a cupboard above my prep counter, which would cause a health inspector to have a coronary, I don't clean the door seals on my microwave daily. I use both a bristle brush and a scrubby sponge to wash my dishes, and I rinse my produce under the tap, instead of soaking it in a sanitizing chemical.
Yes, I think it is important to have standards for a restaurant, and some are non negotiable (servers washing their hands after using the rest room), others I give a pass to (on an internal audit I once had to mark a kitchen down because a sole tomato in the fridge did not have a date label on it). Then again, I am also a firm believer in the 5 second rule when I drop my food on the floor
