Hardly anything unless in a major city, no way to easily tell if there is any coverage other than randomly clicking until it shows, also doesn't tell you the date taken.
Google street view has the 2d overlay letting you know where there is coverage, shows the date taken along with previous imagery, and they have coverage nearly everywhere in the US at a least, although some of its pretty old.
Apple Maps does seem to have more up to date satellite / aerial imagery though.
Hard to overstate how valuable all that street view coverage is on the Google side.
In areas with partial coverage Apple Maps has basically the same overlay showing where Look Around is available. It just doesn't have a great indicator as to why the option is greyed out when there's no coverage.
My little Swedish village has full Look Around coverage, and clicking on the ⋯ icon shows an “Imagery” menu item that tells me the month and year the coverage was last updated. I think you’re underestimating where they’re currently at.