enTourage eDGe is a good option for academics.
http://www.entourageedge.com/devices...rage-edge.html
It is not light-weight and PDF annotation is not as transparent as I would like but it almost replaced my stacks of papers. Even though the product is very good as it is, the company is working very hard to improve the product, so I believe the product will get better over time.
There is a similar thread that may be of help.
https://www.mobileread.com/forums/showthread.php?t=80881