Personally I pay little attention to network availability promises - all they mean is that you get pro-rated refunds if downtime exceeds them. 3 days downtime is possible wherever you go, and if it happens I don't care a huge amount if I get a refund of 10% of a month's costs or not - the damage is in the downtime, not the wasted money.
What's important is the company's track record, and the likelyhood of that record changing, and from what I've heard Hetzner look pretty good in this area.
