La Baciarlata

In brief (for now...)

You can find many books and websites that contain extensive bios... Maybe I'll write my own sometime, but focusing on their first four years and especially on the pre-Rollins era.
I think you can divide them from the singer:

First they had Keith Morris. Released the first EP Nervous Breakdown ('78). I believe they already had a lot of energy in this incarnation, but I wouldn't define them "hardcore" already.

Then the singing duties went to Ron Reyes. He recorded most tracks of the Jealous Again EP and I believe he appears on the rockumentary The Decline of Western Civilization. The songs of this period are the most hardcore they ever recorded, in my opinion, especially in the videotape version.

Then it was Dez Cadena moment and I believe it was a very short period, before he became the second guitarist. I think it was a time of passage between the punk and the hard-rock influences in their sound, the Six Pack EP.

Finally they found a long lasting singer in Henry Rollins who sang in their first LP Damaged ('81). I heard many California punks of that time complain about Henry's behavior and character: they said Black Flag lost its charge of irony and humour and criticized his violent behavior and his strict mental attitude.
I quite agree and think all this reflects in the music, as well....
However Henry Rollins is an icon of hardcore and represents the incarnation of this music and attitude since so many years, especially outside California and US. Many Italian punks of the 80's still considered this album as the best work from Black Flag and agree with Henry's interpretation of the hardcore attitude.
So, maybe if you gain something on one side you have to go back on the other...

I'm not so familiar with their later productions, but I know they moved away from the punk/hardcore standards of speed... So this change doesn't seem much appealing to me. I believe that this production would fit in the kind of Experimental Fringe that was the foundation of the 90's alternative rock.
Sure it is important and I admire that they were eager to find new roads in their music, but I wouldn't give them a prize for inventing today's rock :P

Recollections and different (if you send them :-) points of view:

Early shows were great; I saw Black Flag play with the go go's. Kids were way!!! more open minded than today [...]
I think Henry from Black Flag had alot to do with wrecking things out here, they had this whole "Black Flag kills Ants on contact" thing going. Attacking the kids that liked adam and the ants.. With tsol we were always inclusive, libertarians and socialists..."Do what you want, like who you want, be what you want"
- Jack Grisham T.S.O.L. -