Seems like 'entitled' is new fancy overused insult world...
Businesses commonly provides better than standard services to their good customers. These customers are often not entitled to them, but they receive them anyway. They might stop being good customers or customers at all otherwise.
Is someone who pays higher than usual price, years in advance and with all associated risks a good customer? I would say yes, and every business should love customers like this and take a good care of them.
Now, expecting to have at least the same level of service as regular customer (be able to preload at the same time in this case) is very reasonable and is not surprising that people feel entitled to it.
The most important reward is, of course, the fact that the game like this was produced at all. It would not without backers. And this is the main reason I do not regret doing it.
But if you look at it from customer perspective, being a backer is dumb decision. You have all the risks associated with being a publisher, no share of profits and unlike the publisher, you really cannot protect your interests.
So, if Obsidian plans to do future kick starters, they should treat their backers well. That means at least treat them not worse than other customers, communicate well and apologize for blunders when they happen.