Well I stumbled upon this really old thread and thought that perhaps I could perhaps share a little about my experience, in case anyone out there's still looking for insight. I am enrolling into Berklee in the upcoming Spring 2013 intake, but had my auditions in early 2011 with the piano as my primary instrument.
I was given a 15-min in another room to allow for warm-ups and prep for 5 sight reading pieces (more on this later). This was grossly inadequate, however, as the instruments in the room are in various states of disrepair.
For the audition, I had to play a prepared piece, and I played the Beatles' across the universe. Initially, I felt very pressurized to prepare a standard classical piece, something I assumed most music institutions are keen on hearing. I went against this, however, and went with a piece which I felt was most telling of my musical preferences/strengths/style. Berklee recognizes the importance of individuality, so as much as a cliche this may sound, it's great to let your identity shine through your chosen piece.
Following this I moved on to sight-reading, and was instructed to play them in numerical order. They are arranged in order of difficulty, #1 being of approximately Grade 1 (ABRSM) standard and #3 Grade 7 or so. #4 and #5 are much different, however, as they are in the style of fake books. For me, this was where the difficulty ramped up, as the chords involved in #4 and #5 contain complex jazz chords involving frequent usage of maj13, aug5, dim9 and whatnot. I wasn't expecting jazz chords in such abundance (the entire piece had little straightforward C/G/F7 type of chords) so if anyone deems their interpretation of fake books to be their strong-suit, it'll be great to at least be mentally prepared for chords of such complexity.
After sight-reading, I was asked if I could improvise (to which I said yes), and after a few bars of free-form improv was given a 3-chords progression to revolve my melody around.
Once that was done they proceeded to test how well I can imitate melodies and rhythms, and for this I had to imitate on the piano a tune which one of the examiners was going to play. It starts off simple enough, what with the examiner only playing 1 bar of melody, but with each round the length of the tune I was to imitate was increased by 1 bar. In case you stumble it doesn't seem to be a cause for concern though, as the examiners seem to just be interested in seeing how far you could go before you stumble.
And....that's it! After that I was brought into another room for an interview, but that was a wholly standard affair.
In any case, I surmised that no 2 candidates face the same audition process - Berklee auditions do not seem to be looking for a specific facet of musical proficiency. Do not be worried about technical proficiency, Berklee wouldn't demand that you play scales/arpeggios to prove your technical worth as a musician if it is not your intention to do so. Even if you are unable to read sheet music, musicality can very much shine through in your other faculties as a performer, and ultimately I'd say that "musicality" is what Berklee is after. Perhaps this realization and acceptance that no individual musician is a perfect whole is the key to the school's dynamism.
In short, if you're intimidated by Berklee's audition process: DON'T BE. Hope this post has been useful!