Installed my 5k kit with relay over the weekend. Install went smoothly, took about an hour. Most of the time was spent figuring our a good way to run the wires and mount everything. Ended up zip tying the main length of wire to the back firewall.
Thus far I have noticed no flickering or shaking during my commutes. The passenger side does seem a bit dimmer than the driver's side, but that could just be me. I don't notice it while driving.