I played veigar on the pbe, here are my first impressions

If you haven't already seen the changes: http://boards.pbe.leagueoflegends.com/en/c/champions-gameplay-feedback/LKAEsmPM-veigar-changes-hitting-the-pbe-soon

Q: I'm mostly okay with this change. The projectile speed is just slightly slower than lee sin's Q (I can't confirm this, that's just what it feels like), so you can land it most of the time. Also, it's definitely possible to reliably get two minions with one Q. You just sort of have to "prune" the minions so they both die to the Q. The reason I say i'm mostly okay with this is because minions can now block your burst if you somehow manage to land an E in lane. I was laning against an ezreal, and I managed to land a stun on him. My W landed, and I would have killed him with the Q and R, but it didn't quite happen. I was confused at first, but then I realized I just killed two minions with my Q instead.

Basically, the Q change is a bit of a nerf for when veigar is in lane, but it's great other than that.

W: No big changes to W, but the changes to E affects it.

E: This is the big one. The .75 delay is just... Awful. The indicator is super obvious (It's this glowy purple ring thing). The only way you're ever going to land a stun is if A: The guy is already cc'd by a teammate or B: He's an idiot and walks into it. I was playing on the pbe, so I still managed to land a few (the people there are... not that good lol.) But it felt awful because my opponent had to misplay for me to land it. Not to mention, it guts his only defense against AD assassins and bruisers.

Oh, and also, because of E's unreliability, W is less useful.

R: Not sure what to think of this one. You could argue that because Q can now get two minions each cast, R needed a damage nerf to compensate. However, Q was already nerfed in reliability because it's a skillshot now. The mana cost reduction and slight cooldown reduction might make up for it... But it seems like you really have to focus on Q farming to make up for the lost damage, and high level veigar players never did that.

These are just my impressions, take them as you will. I'm gonna test him some more.