I'm nearly a month in now and I'm loving it. I'm demoing for the company on Monday with my first project. It's an MVP but it's a nice one and I enjoyed making it. The app is a notifications service to help us communicate about events that matter to our internal services, I built it using Pliny. site 
I used Pliny for my starter project during the application process and was a bit confused at first but managed to stumble through it. I like that it's opinionated and uses some patterns (mediator pattern, among others) that encourage me to make conscious decisions about where I put code.
It's a testament to Pliny I think that I was able to ship a working MVP in 2 weeks despite having just started and having to deal with all of the associated new hire nonsense (and buying a house).
I'm not sure that this sort of page adds much value but I'm going to keep writing here to keep track of my progress at Heroku. Much like when I first joined New Relic I'm seeing a rapid expansion of my skill set. I'd like to try and quantify that progress somehow but I don't have a particularly good way to do it, so hopefully this will help me look back and do some analysis.
August 2015 Successes: Learned a lot about the Heroku infrastructure, shipped my first app, did some good pairing and made some great improvements to my personal build scripts with Boxen. Bought a house while starting a new job! We close on September 7th.
August 2015 Challenges: Working way too much, I get up around 6am to be online with my coworkers in disparate time zones and intend to pack it in by 2, but I frequently end up online at 6pm or later. I'm not spending enough time with my family or taking breaks, I need to stand up and move around more (or at all). My RSI is back with a vengeance, most likely because I've been hunched over the laptop screen and I haven't been using an ergonomic keyboard.
September 2015 Goals: Sleep more, 5 or 6 hours of sleep a night is not going to cut it if you expect to be rested and mindful. Take two breaks a day and play with the kids. Make 4pm a hard stop for work, more than 10 hours a day is not sustainable. Order a walking desk and address ergonomic issues.