I can understand an app joining appsumo being in development, lacking features and/or be a bit buggy. Most of the cases are in early stages. I get this and actually I helped some of them in the past and even now as i'm writing this. I get it, that's the game, see the potential and jump in.
What I don't get is being rude and deciding to carry one with their life while they costed me time (money will get back, time I'm not) and came close to lose a client.

Platform unable to deliver a proper run, Said guys don't worry, we'll get it sorted together.
A few hundreds credits burned and never reissued. Didn't bother.
Not supporting Greek fonts, asked kindly to get it corrected.
No reply till the day of my meeting with the client who got pumped up. Had to apologise!
Next they told me to chose 1.... hear hear chose ONE TEMPLATE TO ADD GREEK TO because engineering is busy with other languages.
Spent my last sanity drop and asked them to suggest a monthly deliverable, so I know how many licenses will have at the end of each period and plan accordingly.
Oh man, I want so much to start talking French now bit I need this to go out.
no response, after another two follow ups. I might need to hire a person just to deal with Vidyou.

Calling out app sumo here, there should be some bear minimum you can guarantee. I'm an old client back from the damn start when Noah left stupid FB. Being around since then. Don't expect a random company with false promises to break this relationship.

If they treat a 6-stack like this for asking font, F O N T S, what else to expect.
Avoid dependencies with this service at all cost. Plain liability.