Switching between dthrow and upthrow at low-mid percents seems to be pretty important imo. There are a lot of situations that dictate which throw is the better one. uthrow > fair (~22%) does more percent, but dthrow > fair (~17%) gets you to the ground faster so you can pressure the opponent easier. Not to mention back throw to fair (and dragon rush) is still a thing. So there's 3 throws in your disposal you can use to just mess up your opponent.
I find dthrow to uair really hard to get. Often times the opponent's airdodging through, but I'm still fast falling and being below the opponent to follow with something else. It's just something that only seems to work at certain percents.
dthrow to nair at low percents could work. it does combo if done correctly. the usage really depends on the matchup. like, ur fighting a big, tall, or big and tall body you can try dthrow > nair > utilt x2 / upsmash / rock smash / up b. it doesnt work on small characters like pikachu nor on any characters with bs combo breaker moves like luigi. again this is really matchup dependent.
dthrow to dair should never work... but my God I'm going to ****ing go for it 100% of the time at the ledge anyway because i dont give a ****
dthrow to upb... could be a thing. On Sheik I was comboing her from 85%. But this is in training mode with no DI. Again, super situational, but if you get it you GET IT. Also, you have to dash forward then upb in one motion. Similar to how you get back throw dragon rush where your inputs are back throw, dash forward, then jump side b in one motion. Here's a gfycat of me showcasing this:
http://gfycat.com/FairMiniatureBrant The reason I pummeled was to increase the combo count after down throw.
that upthrow kill percent chart is extremely helpful too.
Did I miss anything?