Posted to UserVoice, as requested.
Arbitrarily rotating the labels to 90 degrees doesn't normally result in a very pleasant chart, in my experience. I either wind up with a very tall chart (proportionate to the rest of the page), or the plot area (say, where the columns of a column chart render) gets compressed to accommodate the rotated labels.
I really just need a way to set the rotation value of the labels on the client side *after* data has been requested, but I haven't yet found any obvious way to do so.
I would love to be able to do something like:
chart = $(
/* ... my magic code to calculate required rotation */