One data point:

I used it for the first time 2 weeks ago.

Meetup.com has calendar feeds. You can get a calendar feed for all the events you've RSVPed "yes" to. You can get individual calendar feeds for each group's events. But there's no way to get a calendar feed of all the events happening in all of your groups.

I'm a member of something like 40 groups. The thought of manually adding each feed as a separate calendar in Thunderbird - and the thought of Thunderbird then trying to cope with the result - was... unpleasant.

So I set up a pipe to combine all the feeds into one. Very cursory googling suggested that Yahoo Pipes was the easiest way to accomplish this.

Fairly slick UI. Unfortunately it turns out that meetup.com apparently serves 503s to requests coming from Pipes.

I used a pipe that created RSS feeds from Google+ pages in conjunction with some other stuff to get all the articles I'd want to read in one document (with a table of contents) delivered to my kindle. I'm now working on something that doesn't use Y! Pipes and simplifies the process.

We all knew it was coming, but the end of Pipes still sucks.