M.,
I would definately shoot for more "formal" nap times, as you put it. When our little one was tiny, I hated to hear her cry, and she quickley got in the habit of napping in our arms, and sleeping in the bed with us (and I mean, fall asleep nursing, and right up next to me). Once I had to go back to work, I had to tough it out with her one night (well, it took a few weeks to really get her transitioned where she wouldn't cry at all) and MAKE HER sleep on her own in her bassinette (we didn't move far!). At this point, she also had very erratic sleep times, and usually only slept because she was so overstimulated and worn out that she would almost pass out from exhaustion. Once we moved her at night, we then moved her during the days, too. We ALL got in a better routine, where her sleep and awake times were way more predictable, and she was overall a much much much more pleasant baby to be around. Not only was she getting more sound sleep, she knew when it was coming, and (still) happily looked forward to it. She's almost 2, and today when we were in the car on the way home, she said "Nap, momma, nap!" It provides a sense of routine, which babies thrive on, and a sense of security, which is a must. We respected her nap times and tried to be home (or at Gammy's) when those times rolled around, and we all did better. Not to say that they have to "run" the house, but let's be honest-- they do! I would try to move away from letting him fall asleep just anywhere, and put him down in his crib when he is good and drowsy, but not full on asleep. Everything I've read and heard (and this makes sense to me) says babies need to learn how to put themselves to sleep-- if they don't know, they depend on you, or the swing, or the car, or whatever to do it for them... so when they wake up, scared, and confused because they aren't sure how they got there, and want to go back to sleep, they don't know how to do it, so in you go, or the swing gets turned on, or a car ride around the block... you get the picture. To me, it's a gift to give them, the skill of good, comfortable sleep they initiate. You just have to be responsible for the where and when of it, and they take care of the how. Good luck in whatever you decide to do!
J.