From: Southern California
Some more playtesting data. Started a Barbarossa scenario as solo Sovs this weekend, am now in June 1942. Definitely harder than the Grand Campaign. I was pushed back to Leningrad/Novgorod/Smolensk/Bryansk/Kursk/Kharkov/Stalino before the snows hit. Had garrisons in Kiev and Odessa that held out through the winter. During the winter I was able to push back in the Ukraine to reestablish my front line at Odessa and Kiev, but am pretty sure a human player could've taken those places before the winter hit.
I knocked out Finland during the 1941-2 winter. Murmansk had to be heavily reinforced during summer 1941 to stop the Axis from taking it. You also need to put up a solid line of corps north of Leningrad to stop them at the isthmus. An active Finland definitely makes things harder for the Sovs.
I had to resort to a fairly drastic tactic: disbanded my entire airforce on the first turn in order to get the PP's necessary to build up the Red Army (and toss some points into research). I've never had more than 300 pp in the kitty at any time in this game. I disbanded a few of the armor corps, too, mostly the ones exposed at the front line on 22 June 1941 that I didn't think I could get out.
In fact, going into summer 1942 I still don't have an air force, heh. If I countinue the game I'll start building it up now, however. At least some fighters. The AI loves to bomb my armored corps, it's getting annying and expensive and unlike 1941, they are in the frontlines now and exposed.
Running around with about 85 infantry corps, 20 armored corps (not fully upgraded yet, maybe 2/3 are at level 3 armor), 5 motorized corps, and maybe 50 odd divisions scattered around. I had a lot more divisions earlier on, but have been gradually upgrading these to crops. Tech is at 3 for arty and armor, and 2 for airpower.
Situation is stabilized and I regard the war as being won at this point, although it will take a while to win it.