The new units are technically good but I don't feel like pulling for any of them; I don't need a bulky enemy phase sword cavalry unit, another enemy phase green mage or a (possibly slower than Linde) infantry blue mage so contrary to my own expectations I might skip the first real FE4 banner.
Sigurd is mostly a defense team unit that will be very annoying to kill in one round, triggering Wings of Mercy often. Players with Nowi or FCorrin in their cores won't be bothered at all however.
I don't expect Deirdre to be a big factor on defense teams after she stops being a bonus unit, similarly to Julia. Depending on stats, TA YTki could still beat her, especially with DD3.
Speed Ploy is very interesting though and it will take me a while to think about the most useful applications - my first gut reaction was Firesweep Est but I myself am not sure how serious I am about that concept.