I'm on App.net
I'm still on Twitter (@paulrouget) and FirefoxNightly as well (@FirefoxNightly) but I can't use Twitter the way I want anymore (see this), so I moved to App.net (@paulrouget). All my post on App.net are synced back to Twitter.
I use Twitter a lot. I use it to promote my own work. To promote Mozilla's work. To gather feedback. To share the latest gecko updates. To get bug reports. I have thousands of followers on @paulrouget and @firefoxnightly. Twitter is more than a social network to me. It's a tool. I use it to share and track ('search') things.
But sharing and tracking is getting more and more difficult. I can't use Twitter as a tool anymore.
For example, I tweet things from the @FirefoxNightly account. And via IFTTT, I could sync the favorited tweets directly to the Tumblr blog. That is not possible anymore. I also used to use the "Search Realtime" feature that is not present on mobile anymore or in the Twitter app (how long before it gets removed from the website). I also used to use the RSS feed. But again, it's gone.
I don't trust Twitter anymore. I will post from App.net now. App.net has been designed to be instrumentalized. So I can sync it with Twitter (where my followers are), Tumblr, and it works well with IFTTT.
PS: I use twapp.phuu.net to sync twitter and app.net. Also, IFTTT works too (twitter forbids only "read", not "write") but it's not realtime.
PPS: there were some polemics about this post. Yes. App.net is not free. You have to pay $50 to have access to it. But, I am not asking anyone to move to App.net (twitter is fine). I am paying for a sustainable/hackable/open tool (see it as a pipe), that let me handle my stream the way I want. So yeah, it's not an OpenSource and free tool. Nor is Twitter. But the service has been designed to let me handle the data the way I want. And for me, this is the most important thing.