I have enough stress in my life right now without trying to beat this game on Classic IM, decided to switch to normal IM after getting my best squads wiped multiple times. Normal, even on IM is so much easier. I'm overflowing with money and ranked up soldiers a couple of hours. I just look at it as an extended tutorial and a chance to see all the abilities and everything. It's certainly not as fulfilling, but it's still a lot of fun. I've only lost like 4 people after many missions.
I'm really digging the variety of maps and occasional special missions. I've seen subways, construction sites, warehouses, streets running with water, fast food joints, a bridge, an observatory, forests, swamps, and on and on. Good stuff.