You need to watch out for crimped primers, 380 brass, and oddball cases with the ledge in them. I figure if you have to to look at each headstamp you might as well throw the brass into piles by maker.
This is sort of what I do as well. It gives me a chance to inspect as cull the bad cases and any .380s that sneak by.
Now rifle brass is a different story all together, and I inspect every cartridge carefully and discard a lot of it.
I used to sort them by manufacturer into about 15 piles or so, but then I realized that about 80% or more of the brass I get falls into 4 piles:
Winchester
Federal
Remington
Blazer
and then I also separate the NATO crimped brass (for reaming, I don't actually see much of this).
And then "other" for all the rest of it, and be done.
That makes 6 piles total.
As mentioned, it gives me a chance to inspect and discard bad cases, or ledged cases, and I can get the NATO cases reamed that need to have the crimp removed.
This is what I see from the range pickup brass in *my* area, you may find a totally different mix where you shoot however.
I am not sure if it is totally necessary, and to be honest, I have been beginning to wonder if it is even worth it for 9mm. I have tried to see if a certain brand of brass shoots better in my guns, but I am not sure that I can really tell a trend with my shooting skill level!