Today I've had more time to deal with the problems and it seems they have been gone.
First I did a full SD FAT32 format under my Windows 7 x64, copied all my ebooks into it and has been recognized by the PocketBooks at first chance. And now it is shown in Exploer like the internal disk (yesterday didn't). I've copied and moved files from and to SD within the device and it has worked well.
I've been reading about 4 hours (one complex PDF, one self-made PDF and one MOBI file) and it has worked like a charm. Turn page is FAST in MOBI but it does not respects all the ebook formatting.
PDF Page turning with Adobe App is good enough, as fast as in Kindle DX. However pdfviewer simply sucks.