My comment is limited generally to the first season, 1959-60.
This superb series was one of the first to be televised in color, and it was highly influential in persuading Americans that they had to buy a color television set, which was about $800 in 1959, the equivalent of more than $3,000 today. How many of us would pay that much for the privilege of watching a show transmitted by a cathode ray picture tube on a 17-inch screen? I was eleven when the series began, and I watched it from the beginning.
Watching it now, 50 years later, several things come to mind. First, many of the story lines involve the Comstock Lode and the heyday of silver mining, which dates to 1859. For 1859, the weapons and clothes are, for the most part, not authentic. (The haircuts are left out of the discussion.) That's basically a nitpick.
And, it would have been impossible for Ben to have arrived in the Lake Tahoe area in 1839 and to have amassed a 100-square mile ranch in the next twenty years. Pioneers were still trying to solve the Sierra Nevada problem as late as 1847, and the Gold Rush did not even begin until two years later.
Indians are not played by Native American actors. John Ford was using Native American actors in the 1920s. The Bonanza producers could have easily done so thirty years later. That is a major nitpick for me.
There are other time-line problems. In Season 1, Mark Twain appears, and he is depicted as a middle-aged man. Mark Twain was 24 years-old in 1859. The stories also vacillate between 1859-1860 (pre-Civil War) and what was more suitable for an 1880 time-frame. There are continuity problems, over and over.
It is somewhat off-putting, too, that there is so much killing in the first season. In time, the killing was reduced.
Many of the episodes take a socially liberal slant, which would be hard to believe, given the time-line, but give the writers credit for anticipating the seismic shifts in the Nation's attitudes beginning in the 1960s.
Having said all that, the acting is good, and I have come to conclude in my latter years that Adam's character was drawn better than any other's. I don't think Pernell Roberts ever got the credit he deserved. Also, Season 1 reinforces the fact that Dan Blocker (Hoss) was a good actor.
Many of the stories trace real historical events. The guest stars were interesting.
This was great family entertainment, and the series stands up very well by any measure.

I remember loving this show when I was a kid. I thought the helicopter was the coolest thing I've seen. It was ultra high-tech for it's time. It could repel enemy fire, do all sorts of acrobatics in the air, and take down nearly anything in it's way. Now I go back and watch it today and am surprised how lousy this show really is. The casts members are hardly compelling, there are a lot of cheesy moments, and the fight scenes are incredibly fake looking. And nearly every ending has the same helicopter fighting crap with the obvious reuse of grainy low quality stock footage. Lot of the footages appear to date from the Vietnam War era.
Airwolf has basically the same theme as Knight Rider, except the crime-fighting vehicle of choice is a helicopter instead of a car. After watching a few episodes, I found myself utterly bored. I do, however, love the theme music.