I prefer the 80-20 grind myself. I will put chopped onion inside mine, the wife doesn't like it. She also likes her burger RARE (I don't).
The bun comment is very apt. I like a good bun lightly toasted. I also like a good hamburger bun.
Other items I vary depending what we have, I tend to like mayo on it, the wife does not.
Long ago I'd buy ground sirloin that really was that and they were great, I keep forgetting to ask our local butcher to grind some for us. His steaks are pricey.
The Whole Foods near us has a dry aging unit in their butchery. I was intrigued. Their steaks are pretty good I think.