I would say: "All good interfaces resemble one another, each crappy interface is crappy in its own way."

On the surface they may resemble each other, but the effort is always in the little niggly details of error messages, page flow, arrangement of things on the page. Whereas crappy interfaces are just CRUD.

But that's bastardizing the original Tolstoy quote, which IIRC was "Happy families are all alike; each unhappy family is unhappy in its own way", i.e. success looks the same, but failure is widely varied.

</pedantic>

Applies to startups too. And oh look, there's a Wikipedia article on it too:

http://en.wikipedia.org/wiki/Anna_Karenina_principle

That page seems to be entirely one author's (Jared Diamond) twist on the original phrase. There's nothing wrong with turning a phrase around - it's akin to irony.

The page suggested that it was also used in statistics and ecology. I'd never heard of it before I Googled to make sure I had the quote right, so I'm basically taking Wikipidia's word for it (always a risky thing...)

Tolstoy!

I stand corrected. And since I corrected the original, I'm noting here that I originally had "Dostoevsky."