I'd say a sure fire signal that it's inferior is if it can be replicated by someone else easily. If so, they can replicate it, then improve it - making the original inferior.

The iPhone looks extremely simple. But it's a ruse - it's actually massively complex and a feat of engineering. It's hard to copy.

I agree, it takes a lot of thought to decide what to leave out - lack of features can be a good thing. But those decisions are not really defendable in terms of IP (Unless you complain Huddlechat 'stole' your whole UI and they roll over)

I haven't used basecamp or highrise extensively, so perhaps they make up for campfire.