Thanks you for the replies.
I do mean to take the reader out with no cover at all. I think the best thing of Oasia for me is its lightweight. With the cover, it would be just another PW3/Voyage/H2O (I think). The no of using hours should be ok if I charge it every night when I go back home at night.
Thanks again. I just wanna get advices from Oasis users before I make up my mind.