The ending sure is... something. I got what I gather is supposed to be the best ending, the "synthesis" one... And I really don't know what to make of it.
To put it bluntly all the endings are not bad, they are just depressing as HELL. Seriously.
In most of them Shepard dies... and if he survives, it just means that synthetic life will be created again, and destroy organic life (as far as I understand). Even though my Paragon Shep spent some significant time proving that peace is possible.
For the "best" ending, synthesis is weird - destroying the mass relays, so everyone in the galaxy is cut off from each other, Shepard dying and leaving Liara (in my case), and everyone turning into weird machine hybrids.
Well at least Joker is happy...
I just feel there needed to be more closure, I guess.