But if you are evil aren't you better than these fools you walk amongst? ( read with Irenicus voice) As @mrfuji3 has said, it's only been implied that there is a downside -- perhaps you can have it all. That's Astarian's plan. Get the benefits without the downside. You always knew you were better, develop your powers and become the ubermench, the apex predator in the herd.
I think people are thinking its only a good playthrough if I could imagine a real person doing it -- but in the realms playing evil is always the wrong choice. Your soul ends up being tortured for an eternity and a brief look at any history book will tell you that evil organizations get defeated more often than not. Be like Szass Tam -- he has sold his soul to an evil god. But he thinks he so smart he can find a way out the deal.
Did your evil character use the gloves, shield and amulet? Did you take the brand? My good characters had to leave those alone.