As we all know that df.HK is now juggleable, I thought it’ll be a good idea to start a thread where people can discuss when and where to use this kick. The timing is kinda tricky so it may be helpful to break any advice is into:
Hopefully this can help guile players that are still learning or just converted from SF4 to SSF4.
Sorry when i post here, but i think its the right place to ask 
How can you combo a DF.HK after a Sonic Boom? I cant get it connect…
Greetings
no, i’d just say learn to use the damn thing. it’s easier than ever before to use.
in terms of anti air, it hits all the big characters (hakan/sagat/honda/abel/zangief/balrog/gouken/rufus ect).
you can combo into it from a bnb ending in a boom in the corner against balrog and rufus
it hits gen’s jumps
it hits dudley’s jumps
it hits m.bison’s jumps
it now even hits shotos at certain ranges when this was totally stupid to try pulling of in o.g sf4.
it hits the majority of characters if they neutral jump a sonic boom.
at the end of the day, it’s such a weird move that you have to learn how to use it anyways. so once you’ve practised it, you’ll be able to know the situations where it will work.
if a shoto does a tatsu we usually just cr. Fierce it but if he’s going to float to the other side, id just wait when he crosses me then whack him with the df Roundhouse into ex flash kick.