As part of this we’re shutting down our business, effective immediately.

That is what happens if you rely as a user on free apps. Poofff and your app is gone. No empathy at Chroma Labs for the user base which made them attractive bait for Twitter, only appreciation for the money offered.

Apparentlly, if you already have the app installed it will continue to work, but you can't install it new from the announcement.

Yes, that is true, but the practice is that it feels very discouraging if you continue to use it.

I was an avid user of the Google Talk app way before they started to push Hangouts and Google used the same tactics, although they announced it beforehand: it wasn't a simple Twitter announcement like in the case of Chroma Labs. The Talk app continued to work, but no updates anymore, no place to redownload it after a device crash or upgrade etc. I felt left alone and eventually switched to something else, and it wasn't Google Hangouts.

Absolutely correct, these are often situations of annoyance for many.

My memories of tweetdeck are similar, when it was acquired by twitter. Tweetdeck had some terrific features, but sanitised by twitter.

It's really surprising how bad twitter is at developing for its users, imho.