Don't agree with all the 10/10 reviews, pure fanB reviews. ME3 is definitely more of a 8.5-9.5 game, I'll judge it myself when I get it later today but that's probably where my rating is going.
This is slightly worrying. (No spoilers)
http://www.pcgamer.com/2012/03/06/mass-effect-3-war-assets-and-readiness-how-multiplayer-affects-your-ending/
So if you want to go back to the game in 10 years you'll have a hard time getting the optimal ending if the multiplayer is dead.
I'm not obsessed with getting the optimal ending though. What's the point in choices and consequences if you're just going to retry until you get it 'right' or use a wiki to look up the best choices?

Never did that with the ME2 Suicide Mission either.
You won't need to do multiplayer in order to get the best ending although doing the multiplayer will make it easier to get to that point.
I playedlike 4 hours of ME3 yesterday and one thing is for sure it's a good Action/story game, but it seems like Bioware has totally lost the idea of what RPG mechanics are and how they should work to make a RPG. In a way you can say ME3 is similar to DA2, heavy focus on combat and very little focus on RPG mechanics. It feels like an interactive story being told, more then you as aplayer controlling the character and shaping him. :/
That's my thoughts as well although I haven't played it yet. Judging from what I saw of the IGN stream it's definitely more autodialoge although choices are still there, just not as much and that's a huge problem. The reason that's a problem is
you lose the ability to roleplay the character and how can you call it a Roleplaying game when you can't Roleplay the character, (JRPG's are an exception, different type of RPG).
The combat has been improved, there is more empheisis on RPG elements such as EXP all the time instead of end of mission like ME2 and the weapon customization but losing the ability to Roleplay Shepard is a much bigger issue then anything else in the game that I have a problem with such as the timed missions. It's the reason why I said that ME3 doesn't deserve all the 10/10 ratings and further proves that the vid game media is useless. Word of mouth is better, seeing 8-8.5 reviews for Dragon Age 2 would probably make you think, "Oh this game is pretty good I should pick it up" but the fan reviews say otherwise and give the game it's true rating. I wouldn't judge metacritic because the score will be trolled early on but the word of mouth from fans will give the game it's true rating eventually.