The only thing that really bothered me about them was that the Synthesis option was so out-of-left-field. We've spent three whole games with the Reapers as the (un)known enemy. We've sacrificed strangers, comrades, and perhaps loved ones, fighting them. Even though I might actually prefer the "Green" outcome for the Galaxy, if I'm being honest with myself and true to the Shepard I've created over those many, many hours of gameplay, there's no way I choose anything but "Red" in that moment. None.
There's just not enough from the Catalyst (the real power behind the Reapers, remember) to make me want to "join" with it. Be gone! And good riddance. Between EDI, and the Geth/Quarian détente, we know that cooperation with synthetics is possible. And it was two humans (Joker and me) who accomplished those minor miracles ) So take that, Mr. "I know better" machine-with-a-child's-face!