Depends on DI. I'd try it on the last stock, only if you know they DI down to recover below the ledge. If you do this often they will catch on. However, if they up b early you can replace the dair with a fair, so that you go
past them, or just DI that way and airdodge, then ledgehog. Very tricky, but gimps bowser and sometimes even DK!
Sometimes if you want to ensure the homing with hit you should bthrow, then run offstage, if all you want is to nail the homing. Another thing that works if they don't immediatley up b and try to recover below the stage is bthrow to forward b to uair or fair. Dangerous though.
Also, for laughs, at early percents do uthrow, see where they are going to land, do up b then do uair as they meet you. Works very well on Corneria on noobs whom don't DI when thrown, and even if they do
you can chase.
Also works if you know where DDD will land his up b. Run there, bravely up b under him and as he bounces attempt an uair!
Uthrow to up b to uair is also great on the top platform of BF.
I think more experimentation should be done on where to leave springs.
For example, if you know you can't edgehog an Olimar at low percent, and he is already jumping back, and there is no time for homing, up b at the edge. He will bounce off the spring most of the time! Works on the falling state of all characters too, when in fall special, and if you miss, big whup, you were prolly owning them anyway!
I wonder if spring would counter short hop dair from Ganon and Spacies? Could you imagine Falco approaching at high damage to dair you, you up b then uair him as he bounces off the spring? Hilarious.
EDIT
Did it on my Wife once or twice, but she's not too good at DI...
Did it on lvl 9 comps set to fight as well to test.
SUPEREDIT
Just tested it on Wario. If he uses bike, he's gone. If he does it after some down DI, sometimes stage spike (FD) if he up b's before you can dair, he'll often not be able to make it back, if he can, it's a simple matter of getting the edge first.
Off to test DK some more.
SUPERA EDIT
Works on DK in really rare conditions, it's actually best to turn your self around before homing so that your dair
knocks him away, not on the stage.