Yeah, I'm not aware of any Arabic texts published on mobi format, or even epub format.. Yet. I'm sure the epub format would do a great job, if taken seriously. Most of my non-PDF texts are English and Spanish, which is alright for me.
I have access to many Arabic texts, and most of them are either TXT or PDF files, or at times DOC (bad choice haha, but easily convertible anyway)..
I think the decision's obvious to me now.
Cybook Gen3 it seems.