I disagree completely. The Isis FH is HARD. I believe that anyone who could get to 1800 with the Isis FH could get darned near 1800 if not all the way there with any other strat.
Even if you have a build order giftwrapped for you, you still have to EXECUTE it. A PERFECT Isis FH will get you to heroic around 7:45. An average one will get you there between 8:15 and 8:30. Suppose you go A/E. 8:15 is PLENTY of time for an Egyptian opponent to mass priests or a Norse opponent to mass Hersir, and even though Greek only has 2 heroes, they do a pretty impressive job on those Ancestors with a few minotaurs helping them out. And what if you get Krushed at 5:00, or Loki rushed at 6:00, or hippikon or poseidon cavalry rushed at 6:30-7? You're not going to get to heroic before 8:30 while you're dealing with all that.
To get to heroic by 7:45 your econ management has to be PERFECT. What if the second food source is far away? What if Zeus bolts the priest? What if you're sending sheep back to the TC and an Oracle happens to steal them and send them away?
Bottom line, the Isis FH isn't about executing a build order, casting A/E and saying good game. You still have to scout for food. You still have to be prepared for an early raid. You have to be able to cast A/E at his TC and be ready for the possibility that he was waiting for it, and if your ancestors disappear you have almost NOTHING back there at home defending you. You still have to know your counters.
Those of you out there who are able to Isis FH before 8:00 9 times out of 10, you have my deepest respect.