Good points. I visit more or less daily too; for me it's more about the quality of the content than the uniqueness, since there's little overlap between who I follow on each. I only visit Facebook maybe once a week and Twitter once a month or so.

For me, G+ is where I post things I find interesting, usually links and thoughts to a relatively limited audience of real-life friends and acquaintances, and sometimes tech-related thoughts to my Hackers circle.

At this point I only use FB for a) chatting with people whose phone number / email address I don't have, and b) to keep in touch with and get updates from more distant family/friends (e.g. "that waitress I worked with a few years ago got engaged-- best wishes!", "it's my buddy's college roommate's birthday-- let's go get a beer in Portland sometime this summer!")

And I only use Twitter to read jokes from wannabe comedians and publicly bitch about corporations...