So far, I think I like the new melee system - although, yes, it is kind of awkward to be holding a block button that no longer exists to do some combos.
Personally, I'm hoping that the combos themselves receive an overhaul as well, and no stance is left with two combos, one of which being the basic E-tapping combo. Stances like Brutal Tide and Pointed Wind have this kind of situation going, where the stance really only gives one combo as a result.
Digging the instant swapping, though, and the aimed slams are great. Making Channel toggle persist even when not using a melee weapon, as long as it's activated once, is awesome; I use Life Strike extensively, and being able to have that available without the delay of switching and then activating Channeling will make it even more useful for me. Instantly equipping the melee weapon also makes the Telos Boltace's spin attacks much more useful; before this change, the T!Boltace could only use Stormpath when fully equipped, which crippled their utility. With the new system, Stormpath can be accessed at essentially any time. Locking Exodia Contagion to aim-glide is...annoying, though. Before, I could use it by incorporating bunny-hops into my strafing, keeping my distance while I bombarded enemies, but with the aim-glide requirement, it forces me to move toward the target and delays my landing.
Calling back to hopes...I hope that Charge attacks stop requiring the pre-attack swing. This limits the usefulness of Glaive throws, the Caustacyst, and other weapons with special Charge attacks, by making them less responsive. On that note, Glaive throws should also just be normalized to the dual-wielding throw mechanic, in my opinion.