9.1? I thought development stopped with 9.0, so that is an improvement.
Mostly the UI. Expect erratic scrolling on many screens, slow screen
refreshes, in the text area a cursor that is a little bit off from where
it actually sits.
Particularly for parsing the last few versions (9.2 and the current
alpha 9.3) brought a lot of improvements and bug fixes, so you won't
benefit from them. In practice this means more crashes, less information
when parsing (particularly when it goes wrong), and sometimes erratic
behavior. All in all, parsing goes a lot slower than under Windows.
See what happens, and if you can live with it, and if you have plenty of
time, you may appreciate the work that went into providing a version for
Linux. But for me, the performance of FLEx was the reason why I switched
back to Windows five years ago. This is by no means the mistake of the
developers - they had to work with a software base (called Mono) that
imposed all these things on FLEx, and from which they could not get away.
Andreas