For what its worth:
I have been goofing with a Mongoose IBOC that was originaly sold at Target. I don't have more than 20 miles on it. (An aside I did not buy this bike, it was left over when a co-worker brought me 3 bikes to make two.) It riides OK but I have replaced these parts on it:
wheels
seat post (to short for the average adult male)
rear derailur
front brakes
Will be changing soon:
crank and chain rings
front derailur
So it rides pretty good and only needs a few things replaced. Oh I havent broken it down to see what is used for the bushings in the pivots. I don't expect them to last long.