I have lots of good rock, but 'Whipping Post' has got to be ranked #1 for the most awesome rock guitar playing. Followed by 'In Memory of Elisabeth Reed', 'Strasborough Blues' and 'Mountain Jam.'
We lost Duane Allman much too soon. 
A major classic concert(s) and a landmark live recording. There is a alternate remastered release of the same material: "The Fillmore Concerts", which subtly reduces the somewhat over-emphasized guitars' prominence in the mix, and also includes the live material from Eat a Peach, as well as an alternate take of 'Elizabeth Reed' (IIRC they felt that the different sections of 'Reed' were better at different sets and had trouble deciding which to include originally.) In this version they used modern digital technology to 'splice' the two performances, which I have mixed feelings about, as technically it's not 'live' in the sense that it's not what the audience actually heard. That's the only song they altered in that way though.
For obsessive 'completists', there is also a six-CD set 'The 1971 Fillmore East Recordings', which includes all four concerts (two shows/two nights) in their entirety, which I have not heard. I'm not that obsessive and suspect they probably chose which versions to release for pretty good reasons.
'Fillmore East' monopolized my turntable for months back in the day. I even had the Nautilus half-speed-mastered version back in my vinyl-spinning days. Some of my friends from back then would probably still have to leave the room when they hear the opening riffs from 'You Don't Love Me'....
