I have the S90XS, bought it when it was first released as the best thing since sliced bread for live work. It seems that Yamaha just forgot all about it immediately after, you don't even see it mentioned in forums. Very dissapointed with Yamaha over this so my next master keyboard is not likely to be a Yamaha, I want something that has a future.
I must say that I'm not dissapointed with the performance of this board but the fact that support for it is non existant.
I'm confused by your disappointment. Specifically what support do you feel is lacking?
Perhaps you're unaware of the support that is
Is the Operating System (firmware) of your S90 XS the most recent? To check and/or update:https://usa.yamaha.com/support/updates/21002_en.html
Numerous downloads for the S90 XS:https://usa.yamaha.com/products/music_production/synthesizers/s90_xs_s70_xs/downloads.html
S90 XS sound libraries:http://shop.motifator.com/index.php/voice-libraries/s-90-xs.html