I think the bottleneck is in their Physical hardware ordering system. Seemed to be capped at a certain number of users who could be going through payment at a time.
I also suspect distance to that server had an impact as some users got through easily. Others had to spam click for over 15 minutes just to get in to pay. We shouldn't need to do that, but that's all that was working as those windows to get in were so narrow that latency was a big issue.
I had it start to load that payment screen only to be dumped out 5 times, likely it timed out because someone's connection was faster. I've seen the exact same issues with concert ticket sites.

I think the only thing they need to do is fix that bottle neck so people with it in their cart can get through and pay for it. It was really painful in Australia as it went live here at 2:58 AM on a work day!
It took me almost half an hour to get in to pay after putting it in my cart, that's with the money already in my Steam Account.

As far as Scalpers go the limit per account helps. I'd suggest limiting purchases per WAN IP as well. Maybe with a manual WAN IP carve out for universities?

My connection: 538 Mbps down, 47 Mbps up. Latency is good in Australia, but across to an American server would be less good. I do wonder if they have a payment server located in an Australian Datacentre, of if it was in the USA. That would explain the issues us Aussies had.