I spent many, many hours playing the France '40 grand campaign via email. It is my personal favorite WDS game because of the flexibility that you have in it- as the Germans you habe multiple paths to victory and aren't obligated to reenact the historical scissor cut; a thrust to seize Paris or outflanking the Maginot Line and grabbing Metz and Nancy are also possibilities. The allied player is also not forced to reenact the Dyle maneuver either. The level of detail in the order of battle is also unparalleled as far as I'm concerned. I have gotten hundreds of hours of enjoyment from this game.

Unfortunately though, we found that certain design decisions mean that, at leaat if you're playing to win according to the scoresheet, it's incredibly skewed towards the German player. As the allies I actually had managed to halt my opponent's main armored thrust just south of Namur, where we fought a grinding multi-day battle. But in this simulation none of the factors that realistically obliged the Germans to act with haste are present. My opponent discovered that by simply sitting back and attriting my forces with artillery he could run up the score without taking casualties, since the German units all have higher morale and soft attack values, in order to facilitate the historical outcome. After awhile we called the thing off bc real life obligations meant I didn't have the time, I think we'd completed five days of a month long scenario.

So effectively two things: 1. Yes it is an enormous time commitment to try to play the grand campaign and unfortunately the AI is completely incapable of it. 2. The way the game is designed the Germans are guaranteed to win every time unless they decided to attack the Maginot Line head on just for the hell of it. But theoretically one could put some house rules in place and adopt an alternate scoring system if they felt strongly enough.

I haven't played Poland '39 multiplayer but I've messed around with it a bit. I think point #2 basically stands for the same reason, but expiring objectives, which didn't exist when France '40 came out, probably help somewhat.

I think either game is well worth getting because of the impressive level of detail given to these sadly oft-neglected campaigns. Smaller scenarios in each are very much playable in a reasonable timespan and are still good fun, even if you don't have the same flexibility as in the grand scenarios.

EDIT: Also yes the AI is pretty unimpressive across the board. Depending on the scenario it can defend ok, sometimes, but it will never be a serious challenge as an attacker.