Rather disappointed by the AI not being better at challenging an human France.
Started my first game with daim in 36. Playing France I expanded the Maginot line to the sea with a Calais trap (instead of fortifying Dunkerke, I fortified Amiens and Dieppe so I could encircle germans in Calais when they come, cutting their supply in Ghent or Dunkerke). Things happened historically untill 1939 (except Japan conquering whole China around end of '38).
When the war started I realised the german AI wasn't more prepared than vanilla AI against an early french raid, so I conquered the border provinces then took Stuttgart and the Cologne region cut from supplies (I destroyed about 8 divisions there) and some other provinces with my Maginot line army (although it was rather weak has most of my efforts had been on the affermentioned fortifications) when they invaded Poland. I even succeeded to take Munich and Nuremberg for some days with cavalry scouts disrupting german production there for some months.
The german reaction was somewhat better than in Vanilla, as two armies of about 16 divisions each arrived to retake the provinces before they finished Poland (when in vanilla Germany seem to be unable to do two things at a time, and concentrate all the forces against Poland untill victory). I lost my 3 or 4 most advanced divisions (not a great loss : all french cavalry) that were unable to reach Sarbruken and Stuttgart during this counter attack. But while the AI retook most lost provinces early, it still letted me keep the provinces bordering the maginot line for half the winter (bad weather helped me to win several battles in november and december, and it's only around end of january when all their forces where back from ex-Poland - which resisted rather longer than usually - that germany pushed the french back to Maginot line).
When the germans attacked the low countries my line of new forts (Reims, Valencienne, Amiens, Lille, Dieppe) were level 7 or 8 with about 8 divisions on each (except Lille where I had my main army of 25 divisions + 5 garrisons) + reserves armies of 5 or 6 divisions in Chaumont, Compiegne and Lyons and unchanged garrisons on the Italian border (+ some militias to keep mediterranean coast). Many of my troops were still '36 infantry as I focused on production with no more than 3 or 4 IC on upgrades (I had researched infrantry up to 41, but they weren't already out). Considering the insane german numeric advantage, I was afraid at this point thinking my defenses would be unsufficient to stop them (by the way had german concentrated 70+ divisions against Reims they would very probably have pierced my line despite the level 7 fort and the weak belgium divisions refugied there in addition to my forces). To slow them I set all my bombers (and the Belgium and Netherland ones -only countries I military controlled in this game) on logistical strike in Flanders/Wallonia.
But reaching the french border, the german just decided it was time to replay 1914-1918. They don't even tried and failed to assault my forts, they stayed with huge armies on the neighbouring provinces doing nothing for a month or two (letting me time to add one more fortification level and have my first infantries '41 out). They don't even advanced to take the undefended Dunkerke before a month (at this point I thought that the AI was clever, and realised it shouldn't advance too much as long I owned Lille, threatening Ghent).
But it wasn't even that. Around end of august, 25 german divisions advanced in Dunkerke, then Calais, exactly like I had planned since the beginning (to pull the germans I just had to retreat my Amiens army to Paris, then go back). While the AI had let about 15 divisions at Ghent and Dunkerke, a double diversion (simultaneous attack Valencienne-Mons and Dieppe-Calais) allowed me to make them move as I wanted to. Then I attacked Ghent with about 25 divisions against 10 supported by my full navy firing on the beach (and the english navy coming to my help too), cutting about 35 germans divisions from supply, and finally destroying about 20 (the AI was efficient at counter attacking and only lost the most advanced infantries, its armored divisions piercing back with the Dunkerke army).
Then the AI entered the 14-18 mode again for whole autumn and winter, my only surprise compared to vanilla being the appearance of a 15+ divisions german army in Turin and some real attempts by the axis to take Grenoble (by chance, I had just reinforced the Armee des Alpes before and helped by snow succeeded to repell the assaults). Italian AI also managed to take Marseille (only defended by some militias) for some days, but was pushed back to the sea by a counter attack of the 4 or 5 reserves divisions I had in Lyons.
Germans were more successful in Norway than usual (debarking two mountain divisions wasn't sufficient to stop them, unlike in vanilla they came with more than one corps) and conquered the whole country before winter. Italian AI was a little more successfull than usual in Africa too, pushing the english to eastern bank of Suez, while taking Tunis on the other side (but in the meantime I conquered Ethiopia with my two Djibouti divisions reinforced by some indonesian netherland troops). But by the second half of 41 italians started losing everything they had conquered, exactly like in history/vanilla, english retaking province after province with armored/motorized forces debarked in Tunisia, while they are also at war against Greece. Germans didn't helped them at all, too busy garrisoning our huge fronteer. Around march 41, they advanced a second time to Calais, but letting more divisions behind, so I couldn't succeed to cut them from supplies again. They also finally attempted one (!) massive assault on Reims in may 41 with about 60 divisions, but far too late to succeed (the fort now being level 9 and garrisoned with 15+ '41 infantry all with advanced artillery brigades stopped them without problem) and some smaller in the south (they took and lost Nice several times).
In 1942 (while USA and Japan are still strangely out of the war, perhaps because Japan-China war ended too soon making the USA never embargo japan or bugging pearl harbour event ? I've not really investigated the events file, but it's probably something like that) war started between Germany and Soviet Union, and it seem the germans weren't at all ready for that, losing 7 or 8 border provinces in the following weeks. Now their troops are starting to leave my border, and I will probably be able to easily free the low countries and invade Italy (which just keep 3-4 provinces in the Alexandria region in Africa) around summer.
Bilan, AI looked slightly better than in vanilla, but there wasn't that big of a difference (at least germans seem to absolutely need to succeed their conquest of France to be able to do anything later and perhaps be better than in vanilla).
ps : anyway I voted "good" because considering how bad is the vanilla AI even little improvements are good to take.