Just out of curiosity, why do you use 37 Signal products? I think their "Getting Real" manifesto is solid, but don't understand why people pay a monthly subscription when there are better and free options available e.g. Google Docs. Is it just the skinabilty so it looks like you have your own site or is there something I'm missing?
If by "better" you mean "more featureful", then you don't have the right definition of "better."
Their marketing is brilliant.
Google docs is good for some things, particularly working collaboratively on docs - but fall short on things like shared messages and to-do lists. Basecamp is just so easy, and the price is so low for a business that it is worth the 40$ a month.
And you're comparing Google Docs to which product by 37 Signals?