Was there Oct/Nov 05.
Carnet, compulsory local insurance and (cool green) local registration plates delivered at the border. I had a visa as I got there.
Traveling alone - not at all a safety issue - very nice people, very welcoming and open. But seeing someone by himself will seem odd to most (I travelled back on my own due to my cousin's tired Africa Twin deciding to do the return journey on the back of a pickup - I had no problem whatsoever, but had often to explain how come I was travelling alone).
Guide - none needed, although strongly expected by authorities. Once you get south (Sabha and further, you will need a guide, particularly if you intend to go to the Fezzan / Akakus - and if you do, do not underestimate the desert - so take a local guide - I had a fantastic touareg).
Man, just telling about it makes me wanting to go back!