Not a fan.
No dual implement spellcaster unless they pick up arcane implement proficiency or swordmage multiclass to be able to use their heavy blade as an implement.
Despite being a weapon user, they are denied weapon enchantments, and have to stick with rod/wand enchantments.
Their striker damage feature only applies to warlock and warlock PP powers, so no dipping into other classes, no bonus to racial powers or PP's.
No Curse, no Prime Shot, no Shadow Walk, almost all existing warlock feats are of no use to the hexblade.
I would much rather play a regular warlock, and make my own hexblade with Eldritch Strike, and/or make pretend melee attacks with Shadowdance Armor.
The only somewhat interesting part of the class for me is the summoned critter, but even that is not enough of an attraction to play the hexblade. I'm rather disappointed with the preview. Will have to wait and see the full class write up and any new feats to pass final judgement.