Here:
http://www.the-ebook.org/forum/viewtopic.php?t=19171 I've published an instruction on getting root on 60x/90x.
Partial translation:
1. Connect your device to PC
2. Extract
http://www.multiupload.com/A49K088F4J to the root of internal memory on device (so files would get to /mnt/ext1/applications and /mnt/ext1/system/bin)
3. Run get_root.app
get_root.app would connect to WiFi and launch FTP and Telnet daemons. So you can connect to your device from your PC via "telnet <device ip address over WiFi>" or "ftp://<device ip address over WiFi>". No password would be asked.
If you don't have Wifi - you can get a root shell in pocket term. Just launch poterm, type there: /mnt/ext1/applications/get_root.app and after several seconds you'll get a root shell (type "whoami" to check that you are root).
Note:
Be very careful while playing with root rights on your device! You can remount system partitions as read-write and you can easily destroy them by mistake.
Uninstallation:
Just delete the files or format internal memory.