[aloe_falsa]

That's exactly what ruined it for me. The few apparent survivors of the human race are huddled in a tin can, running out of resources - fade to black - and suddenly, by divine providence and author fiat, everything is fine. It kills the suspension of disbelief.

[LordN00b]

...and 5000 years! That's 2.5 Jesus's of time and distance.

[MrDresden]

... and comes accross as a deus ex machina transition.

More authors should be brave and have their stories end bleakly.

Great examples that come to mind would be 'Death's End', 'Echopraxia' (to a lesser extent also the prior 'Blindsight'), 'Consider Phlebas', just to name a few.