It reached the reddit front page for a day, and earned £3,000 during that day. Since then, it's averaged ~£150 per month, with only small input from me (minor updates)
I then saw the traction the blog post was getting, so wanted to capitalise on that quickly. I had an Android phone, so for simplicity (and ease of monetisation) decided to write an app for that. From zero knowledge of Java it took probably 30 hours over a weekend to get the app out, then perhaps another 10 hours over the next week on a few updates and bug fixes.
Getting the app up and running was relatively simple, most of the time was spent looking up API functions in Google's SDK documentation (and SO!). The only complication was making sure the CPU-intensive parts ran in a separate thread to avoid locking up the UI, and dealing with different device display sizes and resolutions. Everything else (dealing with input, generating images etc.) wasn't particularly difficult, but did take time to implement.