I've been sorting nickels for a while, along with pennies, dimes and halves. Here's my take:
Pennies: I get about 15% copper pretty consistently, with the occasional box at up to 17% (though one box had 4 rolls of 1979s, but that's an outlier). I usually get about 8 or 9 wheats per box. I will continue to do this sorting whenever I want a change of pace. I've got over $150 worth of pre-'82 pennies. I also save the '82s, but don't sort them as it is a giant PITA - someday I'll sell 50 or 100 rolls of them on fee-bay to some soul with a sorting machine and let him have the fun.
Dimes: I've gotten skunked on every BWR that I've searched, save for 1 solitary Rosie (we're talking about 12 boxes). I got 2 other Rosies from some CWRs. All in all, not worth it for me.
Halves: I've gotten a bunch of 40% and a fair amount of 90% searching these, and I'll continue doing it whenever I've got the spare funds to buy a couple boxes at a time.
Nickels: I search for war nickels, buffaloes, 2009s and anything before 1956. I get something out of every box (one exception - the entire box was brand new, so I saved 10 rolls). I usually save a couple of rolls per week, and I'm up to around $200 of plain-Jane nickels. You can't lose with it from an investment perspective, plus its a good (if rather inconvenient to carry around) source of extra cash in an emergency. I don't think that junk nickels will ever be the huge score that 90% silver was/is, but we're living in 2012, not 1965. I'll take what I can get, and the nickels will ultimately be a good investment. FYI, I've gotten roughly 1 war nickel or 1 buffalo per box, though the present box I have had one of each (and I'll finish tonight). I've also gotten a 1910 V nickel (on the end of a roll, no less!), as well as a 1938-D, 1938-S and 1939-D. No 1950-D yet, but I know it'll come. I really like the fact that you can just use $100 to have a box worth.