Since they've added the last bit it is now visiable to the naked eye!
I've managed to catch it a few times on fly-overs in my area, and it's pretty neat to see this manmade thing up there in space.
You can visit
Heavens-Above where you can access viewing information. Just select your viewing location & time zone. They then show you all the times and instructions for watching all the flyovers for the next 10 days.