Since my name was mentioned, I'll put in my two cents...
Thank you Don Starr for all your software
Thanks for the kind words, but I have to admit that I (subject to the caveat that I have not seen the entire dialog) take Gommert's side in this.
I (like Gommert, I think) make my software available as fully-functional, 30-day, free trials. During that trial period, the potential customer is expected to evaluate the software and see if it's to their liking. If, and only if, they are satisfied with the software should/may they register it. In fact, one is required to click a button on my web site declaring that they are satisfied with the software before they are permitted to register.
If someone came back to me after registering and said they were unhappy with a feature (or lack of a feature), I would do two things... First, I would check to see how easy (and reasonable) it would be to add/change that feature. Second, if the mentioned feature was difficult (or unreasonable) to add/change, I would state that to the user. If the user then complained, I would point out that the user has already agreed that they are satisfied with the software's performance. I most definitely would not accept "blame" for a feature whose omission the user has had ample opportunity to discover before registration.
An example might be "printing". Win500 does not have a "print" feature. If someone registered Win500, then came back to me a while later upset because Win500 does not print, I would probably first respond with something to the effect of "no, Win500 does not print". If the user persisted, I would probably/eventually degrade to "too bad; maybe I'll add printing at some point, but you did, when registering, say you were satisfied". I almost certainly wouldn't offer a refund or promise an immediately forthcoming "printing" addition.
To some, this may sound Draconian. However, it's a far sight better than most software "purchases". Here, at least, you're able to try the software before you "buy" it, and should only buy it if you like it. With most software, you're stuck after you pay - at best, you might get some kind of "store credit", but you're almost never given a refund for opened software media.