Okay, after a few days of use I think I can give my opinions. What I heard about it being hackable does hold true to some extent. It runs linux and you are able to access kernel sources for the device (https://github.com/pocketbook-free/kernel_613)
and this site (http://users.physik.fu-berlin.de/~jtt/PB/)
claims you can run some other programs on these devices. I just want this for reading so I probably wont bother but its nice to have.
For storage, there is no account requirement like there is on I think newer kindles and kobo e readers, you can just mount the e reader as mass usb storage. SD card slot is also on the outside so you can easily insert and swap expandable storage.
Battery life, well on a few days I can't say much but its only dropped about 5% this past week. Keep in mind the battery is probably 5-10 years old at this point, doesnt seem like anyone has opened up the back of this device.
For reading itself, its a bit slow to start books but it's snappy once you load it. Tested formats are CBZ, PDF, MOBI, EPUB, and DJVU and PDF is the only one thats shitty. However thats normal for ereaders.
It's overall not a bad machine for like the 10 bucks I got it for.