A couple notes on Hylian Shield:
-IT BLOCKS MEGAMAN'S FSMASH!?!!? Y'all probably knew this. It's a projectile, so it's implied. But IT BLOCKS EVERYTHING (if it's a projectile).
-It doesn't block in the "crouching" animation (i.e. the "going to one knee" animation--it blocks in the "crouched" animation itself).
-The lag from shielding, as well as the sliding backwards animation, have both been nerfed.
-Walking, standing and crouching might seem awkward for maneuvering, but with his massively buffed back dodge (the L-targeting backflip *squeeee*) there's very little time where he's vulnerable. Frankly I feel his forward roll is mediocre in this rendition but it then gives you access to his back flip *squeee*
All this together imo makes Hylian Shielding a viable tactic versus campy characters, and combined with Link's own versatile projectiles and his zair makes him (again imo, which should be taken with much salt) very strong versus campy characters. You should be able to force approaches out of them in most situations at the very least.
Sheik needle spam seems very prominent as a tactic atm so you should at the very least be able to force Sheik approaches with Hylian Shield. Not like Sheik doesn't want to get in on you, but at least Sheik will have to approach on your terms and pretty much has nil spamming capability versus Link from neutral positioning, which is always something positive.
I've only been playing the demo, so I can't vouch for the Shield versus the entire cast, but that's my impressions so far.
Oh, and iirc there seems to be a strict window where dash attack (the L-targeting jump slash *squeee*) can be comboed into from a boomerang hit. Spacing and timing both seem to be pretty tight.
Also, if Mario doesn't DI properly you can dthrow>dair spike him around 40-80%. Might be a true combo on bulky heavyweight characters at certain percents.
From what I can tell backflipping should also be a great way to disengage because between it's invincibility frames, its spammability and the Hylian Shield's defensive options you should be pretty safe from anything except direct physical moves.