See people are having problems because they are using him the exact same way as before. Its their fault for assuming he will play the same when its painfully obvious he cant anymore.
The Q can now farm 2 minions at once or one minion and poke the enemy champions. This is overall better then before, its not hard to hit the Q its got a huge hitbox actually and the double stacking allows you to get huge amounts of AP. My friend had 750 AP at 20min with only Morello's, needless to say he was hitting people really really hard.
The W is better overall too.
The E can no longer be used to instantly 100-0 someone anymore. This is sad i know, but now it has a different use. It is really good for disengaging and zoning, it also works really well against someone with no or limited mobility. Veigar was never good against high mobility targets so i dont understand why people are blowing up about it now... It also really helps with landing the W even without stunning them, if you can place both to force them into taking the damage or the stun then you can still 100-0 them (specially with the ability to gains large amounts of AP).
The R nerfs were probably uncalled for, mostly because double stacking AP isnt ideal 80% of the time. It forces you to push the wave pretty hard and the delay on his Stun does make it difficult when you are ganked.