The data.tar.gz exploit has been fixed with FW 5.1.0.
The only relatively easy remaining jailbreak method is Method 3
However, at least if the mmcblk0p2_ssh.img diags partition is installed, this method fails at the last step. I.e.: the actual payload gets installed on the main partition, but exiting diags mode is impossible. It yields an error about some xml file missing every time (I don't remember the exact file name, but it's something like diags_info.xml or so). The only way to get out of diags mode is to ssh into it (assuming that it actually *is* an SSH-enabled diags partition!), and to issue "idme -d --bootmode main; reboot".
Can anybody confirm this? If so, is anybody willing to take a look at this, possibly coming up with a revised (probably even final) version of the jailbreak?