We started out giving the doors just a light sanding thinking that we'd rough the surface up a bit in preparation for priming and painting. The problem with that plan was the layer of latex paint that was improperly applied over the oil paint (no primer), leaving it to peel off and gum up the sander. We really weren't too keen on sanding the lead paint - we got a respirator and were very careful - but the sight of lead dust flying through the air (near our garden!) freaked us out, so we abandoned that plan pretty quickly.Our second option was to use a product called "Rinse or Peel" by Biowash, which is an environmentally friendly paint stripper made with orange oil. It's a thick paste that you spread over the painted surface, and I hate to say it, but I really wasn't expecting too much. Imagine my surprise when we went to scrape the door about 15 minutes after applying it, and the paint pulled off in great gummy sheets! We ended up leaving it on slightly longer the next few times (about 30 - 40 minutes) in order to remove more of the paint layers, and that worked amazingly well, taking us down to almost bare wood.
The best part about this stuff is that you can scrape off the top layer of paste and reuse it on the next door (up to 5 times, depending on how many layers you're stripping at one time). It also kept the lead paint well contained and out of the air.
As for the door knobs and hardware, which were also covered in multiple layers of paint, we tried a couple of different things. At Monica's recommendation we soaked them overnight in vinegar to soften the paint so we could scrape it off.
After all this work, I think I'm beginning to understand why the original owner decided to replace these doors with brand new ones instead of refinishing them (okay, only sorta)!