I am... conflicted about this rework. I remember playing against him being super frustrating because he could just put up his cage and either trap you in the middle or land the edge directly on your head, which was so much easier when it was instant. However, after playing him, this delay on his Event Horizon just.... * sigh *. He needed that instant stun to get kills, but landing it was pretty terrifying for the other player. If he's farmed correctly, he's probably going to blow you up if he catches you. Here lies the sticking point for me... how to make his E easy enough to land that it's possible without someone helping you or your opponent being dumb as a bot, but at the same time, not make it so easy to land that it's really frustrating for other players. I don't think the change balances this very well... it's made it a lot less frustrating to the other player, but for Veigar it's become a nuisance. Sometimes, like in teamfights when there's already a maelstrom of particle effects all over the place already the warning indicator is easy to lose in the shuffle, but... well at that point, unless he's master of skillshots, he probably lost lane and isn't going to nuke someone down like he used to.
The changes to his Q, I like a lot. It's a lot more versatile, but requires a bit more skills to use rather than point and click. If you're good, you can line it up and get 2-3 stacks with one shot (3 if you last hit a normal creep and a cannon creep). I've had teamfights where I got double kills with one Q. Thanks for the 14 stacks of AP guys. In lane, you can even stack and poke at the same time if you're positioned correctly. It's not ahri's.... thing where she throws her crystal ball at you, but it works. At higher levels, you can just one-shot caster creeps with it, and with two going down at a time... you get some good stacks. Not bad.
The buff to his passive is much appreciated, because we all know that Veigar synergizes very well with Tear of the Godess/Archangel's staff/Seraph's embrace because you spam Q to farm. Maybe this change can bring him a bit closer to his former glory, but it's still nowhere close to how it used to be. He used to give you the sinking feeling you get when you see someone pick Katarina, Ahri, or Akali, but not anymore.
In the end... Riot has some work to get Veigar back into relevance in soloqueue. I don't know if the pros are doing anything with Veigar... after all, most of the best champs for the LCS are earlier game champions that I've heard of, and Veigar's most powerful move has been rendered pretty hard to land. Like, at an LCS, this thing has to be near impossible to land the stun.