Very sad. He was a great talent and seemed like a nice guy. That track does not seem like an appropriate venue for Indy Car racing - too small for the speeds those cars can generate, particularly with that steep bank. It seems to make them bunch up, and pack racing is intrinsically dangerous for open-wheel cars, especially ones capable of that kind of speed. It's a testament to the integrity of those cars that he was the only one killed - several other cars were completely destroyed yet still protected their drivers.
The person I feel particularly bad for is the driver who caused the second set of collisions which ultimately killed Wheldon. I don't know my Indy cars but he was the first of two white cars driving in close proximity. He abruptly turned toward the bottom of the bank in an apparent effort to avoid the other crashed cars (which he was nowhere near hitting). This caused the chain reaction of crashes that sent Wheldon flying. In my judgment he made a mistake, and one with fatal consequences. I don't blame him - at those speeds minor errors can quickly turn disastrous - but I know if I were him I'd blame myself. That can't feel good.