James Coburn's performance
Overall I would rank it as outstanding even though I do acknowledge that there were some flaws. I give it a very high mark because the one thing that he had to do to make the movie work well he did perfectly. Namely he convincingly portrayed a very competent, grizzled non-commissioned officer who desperately wanted his squad to survive the war more then anything else. A good example of this is when Pvt. Dietz introduced himself, Coburn's Steiner spoke some very harsh words to him but his eyes betrayed a very great concern for Dietz's survival. This emotional portrayal of Steiner really complemented Peckinpah's ability to portray violence. While Peckinpah was a genius in the brutal scene 'demarcation' Coburn's character helped humanize the squad to make you care about what is happening and it gave great weight to the final stand off with Lt Triebig.
On the negative side, his final confrontation w/Stansky fell flat, I believe that the poster bstephens21 hit the nail on the head by suggesting that Steiner was going to lead Stransky into a suicidal conflict with the Russians and did not intend to survive it. However, Coburn's delivery of the line made it look like what we, in the U.S., call a 'buddy cop'. It's as if Coburn in real life is too nice of a guy to somehow give us a hint of Steiner's more sinister motive. Likewise, his total disdain for ALL officers including Col. Brandt was baffling and unconvincing.
Despite these flaws, Coburn gave a brilliant performance for the reason I stated earlier.
(comments are welcome of course)