[quote name='Moxio']Oh, no, finding them is definitely not a chore. Each level has roughly 3 each, and it will indicate if you have missed one or not.[/quote]
Like Mox and CK said, it's not bad -- all you have to do is make sure you've done something with all the sisters in the level before you exit -- it's usually not that bad, as you'll run into them in the course of doing things, mostly.
finding all the audio diaries -- that's a chore.
there's one you can see under some metal stairs later on -- i still haven't figured out how to get under there. =\
saving the sisters isn't so bad, because every so many sisters, you'll get bonus adam.