I'm going to think long and hard before I preorder again, that's for sure. To me, the biggest issue of the end isn't just the plot holes and the fact that it completely breaks away from the established lore of the game, it's the fact that after all the strife, death and effort, you should have just found a sunny beach to live out your final days and let the reapers do their thing, because the end result was the same. All the galactic civilizations were kicked right back into the stone age. Being as that Space Magic Explosion wrecked the Normandy when it caught up to it, what did it do to the fleets surrounding Earth? If it had the same effect, you just killed off the best and brightest minds of the universe, as well as the bravest. All three endings were a failure.
Bioware's cry of "It's art!" is a lot of crap. If I pay an artist to paint me a mountain scene and I get a dirty cityscape, I'm not going to accept his answer that "It's Art!" and changing it is violating his 'artistic integrity'. He's not getting paid.
The whole Mass Effect series is about hope in the face of impossible odds, and the ending is the complete and total opposite of that. That's not 'artistic licence', it's trolling your fans. They deserve every bit of backlash they get for that abomination of an ending.