As to Airgram, I'm worried because I don't see where they charge money. Pushover looks much more reasonable for me. I became wary of "free" — what "free" usually means is that eventually I am either a) bombarded with ads, b) the service disappears because there is no money or c) somebody acquires the startup because of their stellar subscriber growth (remember "free"?). In all cases I am left out and have to re-invest my time into looking for an alternative.
I also noticed over the years that the most stable and trouble-free services are those which I regularly pay for. I'm quite happy with SmugMug and Squarespace for example, even though there are free alternatives in each case.
Funny how this perspective is different from what you hear if you are a startup founder: as a founder, you are supposed to "build something people want", and the rest is supposed to sort itself out. But if you do build something people want, but never charge for it, you end up disappointing those people sooner or later...
jazzychad, thanks again for the frank statements and giving us the time to find another solution!