OK Pedro, I'll bite and start a thread regarding transcriptions.

I feel that playing Bach on the marimba (or works by any of the great composers) is extremely beneficial. Most (not all) of the instruments in an orchestra or wind ensemble have many idiomatic works written by Bach or Mozart or whomever. Every teacher I know of (which, admittedly, is not a great many) includes these pieces in their standard teaching repertoire. The only way we are exposed to them as players is through transcriptions.

The music by the great composers is often a technical challenge on the marimba (ex. Bach Violin Sonata VI, in E Major), but offers us a chance to really develop our musical expression and sensitivity within the technical requirements. Some Chopin piano preludes work well on vibes, but are not difficult, in fact some are easily sight-readable. But the point of these preludes was to develop the pianists' ear and touch for subtlety and nuance, two aspects of music percussionist are often accused of lacking. Chopin's sometimes strange fingerings are specifically meant to accomplish these aspects.

In my experience, Bach is also a good way to practice playing the correct notes. Let's face it, there are some contemporary marimba works out there where the performer could play half the notes wrong and the audience wouldn't know the difference. With Bach, everything is obvious as right or wrong. It's good for discipline on the instrument.

This post is getting long, but I just have to add that there must be myriad reasons why many of the best teachers and players of any instrument include the great past music in their standard repertoire.

I feel its important to study too (unlike what I said in my previous post). I was just saying that I personally did not like hearing it in performance. But true, it IS very important to play it. Actually, I have an audition coming up, and I have to play two minuets from Bach's cello suite in G. It sounds fine, but the more I play it, the more I miss notes! Just like you said, the audience will notice if you play a wrong note with Bach. And also, I am having PANIC attacks, because for a piece that looks easy, I am having alot of trouble figuring out how to interpret it. I have picked up recordings of Rostropovich and Yo-yo Ma, and I still can't decide what to do. I know that in the audition they want to know how I express the piece, not if the notes are right. I think it is VERY difficult to interpret Bach. Actually, in a Percussive Notes article by Ms. Zeltsman, regarding a marimba competition, she said that someone played the Bach Chaconne, and that it was really risky to perform in a competition because so many people have such different opinions about how to interpret it.
~Behzad