I just finished a game on patch 1.61 (with the Merc. DLC) and want to share a few thoughts here:
I played with all original factions and one custom faction on a gigantic map (all random) and set 3 to godlike, 3 to incredible, 3 to gifted and 2 to normal.
The game evolved to a state where I was in an alliance with all parties (including minors) expect the Krynn. The Krynn were able to pump out 5k hitpoints fleets with about 3k missiles all over the map. Since I was not able to ally them, I thought I could kill em with the help of my alliance, but this was not possible. Interestingly, my alliance members were not in war with the Krynn and the "declare war on party" option in diplomacy was not available when contacting them. They prefered waging their own wars (which ironically were incited by myself during midgame). Because of that I had to fight solo and decided to turtle until a technology victory. Sadly the Snathi were faster (2 turns).
This brings me to the question, is the alliance system meant to be like that? What's the purpose of an alliance if my allies do not help me in war.
The Krynn in this game showed that the AI is able to use very strong fleets (I had a tough time even with massive scale hulls). The problem is how they use their superiority. In my game, they insufficiently used transports, they just attacked my planetary defense drones all the time and gave me (or the damn Snathi) time to win by technology.
A few other things to note:
The planet list scrollbar bugged out once.
I had a 2-3 crashes (could be due to switching to 1.61) and one or two low memory warnings (I am using 16 GB ram without a cache file).