I think most people covered it already.
Great writing story line...
Great cross over... into SG-A!
More information on Atlantis/Merlin/Anti-Ori weapon.
Dialing the Super Gate: SG-1 went to Pegasus to dial the supergate. They can't dial out but the supergate can only be dialed into, the Asguard tried to dial out but failed. Why can't the Asguard, who are in another galaxy ... with their way advanced tech, dial in from their galaxy ?? They should be able to find a black hole and have their gate to dial the supergate at will. [Which would make a great anti Ori Ship weapon!]
Time Dialation: Carter says "20 seconds" but since they're going towards the black hole... to be consistent with previous episodes... their 20 seconds will be significantly longer for Teal'c ... maybe days.
2 nukes exploding at the event horizon not powerful enough but 2 nukes exploding in a Hive Ship is powerful enough. Unless the Hive Ship increased the yield... (which should have vapourised the gates.) since Sam & McKay agree at full power the nukes will probably take out both gates.
Morgan-Le Fay - Why would she allow herself to "Replay" ?
+++ SPOILER !!
What does "Merlin's weapon is NOT...." mean ? Not on the 2 planets ? Not in the milky way ? No phased in (ala his research device) ? Not where they must look. See the preview SG-1 Season10... Ben Bowler is holding the Replicator disintegrator... (return of replicators! OR adaptable against Orii ?)