Well to be honest, I liked the game, but it is NOTHING compared to ME2 in my opinion. ME3 is a competent game, but 2 was just pure excellence for me. ME3 seemed a lot easier too, even on Insanity. I blazed through the campaign in less than a week even with my school schedule. ME2 took me weeks, and there were points where I just put the controller down and took the disc out in frustration. Almost every enemy had health + armor + shields/barriers at a certain point!
I didn't have much issue with the ending, but I had issues with other areas as you pointed out. Some of them are technical issues (PS3). Also, the game just felt a bit lifeless to me at times. I have no clue why the took out the loyalty missions from the series. They made ME2 very interesting. I understand ME3's storyline is the 'critical path', but at times it felt bare boned. If the DLC was supposed to make up for that then I guess that's typical of EA. :/
Anyway for me ME2 > ME > ME3
Hopefully the next installment will have more improvements and be more like 2 than 3.
Playstation = The Beast from the East
Sony + Nintendo = WIN! PS3 + PSV + PS4 + Wii U + 3DS
