The LTE version of Samsung’s Galaxy Tab 8.9, sold by AT&T in the US and Bell in Canada, has been rooted by well-known forum moderator Da_G. He even managed to create a kernel that overclocks the processor, usually at 1.5 GHz, to over 1.9 GHz.
Before you go on to root (and possibly overclock) your device, note that this is for the LTE version packing the Qualcomm processor. The WiFi version, equipped with a 1 GHz Tegra 2, has already been rooted.
Now, head over this forum thread with detailed instructions provided by orlandoxpolice on how to root your Galaxy Tab, or have a try with the overclocked kernel. No warranty, of course – only do this if you know what you’re up to._________