I mostly agree with you, but their first sentence ("Like Dropbox...") relies on you knowing what Dropbox is. Which, as you pointed out, isn't good enough for people who don't ;).
Like Dropbox, but behind your firewall.
For many people, that's a sufficient description to get the idea. If not, you have the second part:
File Sync and Share for the enterprise.
Not as descriptive as the first part if you know what Dropbox is, but if you don't it will at least let you know how to categorize the product and whether it's something you might remotely be interested in. Finally:
Free up to 30 users.
Now they've made sure the next most salient point is given, the next thing you would most likely want to know. Everything else is something you can dig a little deeper for, but for the most part you know whether this is something you want to pursue or not. I think it's brilliant.
Even still, "Like X for Y" is far better than "The product you'll love from the people you love".