Power-save mode isn't a problem on my n810. I have power saving set to "On (maximum)" and have absolutely no problems ssh'ing into my tablet from my PC, even if my tablet has been idle for hours. FWIW, I'm using openssh on the tablet.

For file transfer, I just use scp from the command line. If I need to mount the tablet as a drive on my computer I use sshfs. (I use MacFUSE on my Mac for this; I don't know if there's a similar Windows hack to mount a remote file system over ssh.)