Here is my assessment of this:
I am a Kamelot fanboy for the most part. I think they are the pinnacle of what the Prog/Power genre has to offer--the truly elite. And Khan's vocals have always been a large part of that equation. When all this singer drama first started (pre-last year's ProgPowerUSA) there were a ton of haters saying that there was no Kamelot without Khan. Khan is one of my favorite vocalists, both with Kamelot, Conception, and his guest spots.
However, what this shows is that the strength of Kamelot is not solely or even mostly based on the strength of Khan as frontman and vocalist. It is based on the fact that the music is truly transcendental art. Thom Youngblood has written tunes that rule. When they are sung by someone with the pipes to sing them, they sparkle.
For one, Fabio did an outstanding job here. He doesn't "sound like Khan", but he doesn't "sound like Rhapsody" either. Great performance. What I honestly think now is that if Kamelot has to carry on with a different vocalist, they will be just fine. And I trust that if they can find a permanent replacement, that whoever it is that is chosen will be thoughtfully picked and will do just fine.
Also, goddamn, "Don't You Cry" is awesome live. Why hasn't this been a setlist staple like Karma and Forever???