I am interested to see who on the forum uses Heroku.

Please post if you have.

Feel free to share thoughts, advice, questions, etc...

I used it (their free offering that is) a couple time to host / test a few personal Rails apps. Was easy to set-up (on a Linux environment anyways, I don't know about other OSs), didn't really run into many issues tbh.
Keep in mind, I used it very lightly, so take all of that with a grain of salt ;)

I'm doing the same right now with a node.js app, using a linux box.

I used to free version and found it worked fine. Personally if I'm going to write a serious application I'd use a different service. I think Heroku is great for more exploratory applications which have the potential to have a user base spike, or just completely fail; If your user base suddenly grows you won't have as much of a hard time to spawn more server like you would in a VPS or whatnot. Its a nice idea.