Now that I have finished Mass Effect 3, I will say that this game was unbelievable.
To get the true experience, one must run through ME1, followed by ME2, then go straight into ME3. Can you play ME3 by itself? Technically yes, however, I would not recommend doing that. You will miss 50% of the content.
As I mentioned above, every decision made in ME1 and ME2 have some form of relevance in ME3. Some things will be small, like a dialog change, some will be big.
Are there some plot holes? Unfortunately yes. However, they are small and unless your going through it with a fine tooth comb (or pic in the desert-Space Balls reference), you will really not see any.
Presently I would say the most disappointing thing is the error code one would get while trying to import their toon from 1 to 2 to 3. There is an error in the code due to some changes that they made to facial structures and hair and that that does not transfer from 1 into 3. However, Bioware is working and has a fix for a patch. Upon review and approval of this patch by EA, Sony, and Microsoft, the patch will be released and one could then continue with their MC versus trying to recreate the facial structures.
Now there has seem to be a big controversy regarding the endings and not getting the happy peaceful love ending. Without giving everything away in the ending, the endings will not be what would would suspect. One word best describes the endings.
Indoctrination. Not only is the MC battling indoctrination, but, you as a player are as well.
TBH, I think it was basically brilliant they way they did the ending.
"All national institutions of churches, whether Jewish, Christian or Turkish, appear to me no other than human inventions, set up to terrify and enslave mankind, and monopolize power and profit."