I can get a lightly used 880 for fifty dollars or a new 550 for about sixty or a new 520 for about 40. I know retail on 880 is much more but I would have no warranty. Any opinions appreciated.

you're better off getting the 550 with warranty. it also depends on how you like the button layout, i can't stand the 800 series button layout. i've also had many 880 series remotes break down (though others swear by them), so IMO it's better to pay $10 more but have a working remote with a warranty. they all do the same thing.