OK, so the remaining space is mounted on /home/user/$MYDOCS (I wonder what $MYDOC is), not /home/user. Then this means that the other files in /home/user are on the rootfs partition, which is limited to 256MB. This isn't much, in particular if packages don't use /opt for everything. BTW, is it really ext3, or jffs2 (hence compressed) like on the N810?