Yup, and this is what happened for the "proper" driver for the Aurora AONE's, which a random comment suggested was on the way and then it suddenly turned up in a release. I don't expect the devs to come back and comment on every forum post asking for new features, and the "ideas portal" or a clear roadmap would remove the need to do so whilst keeping the customer informed.
It depends how the ideas platform is used - if there's no response to a feature then yes, people are going to get upset and either rant or move on.
If the idea is moved onto a roadmap backlog, then at least people know it's been selected for consideration and can track the progress.
A lot of my day-job these days is supporting large enterprises in how they improve visibility into their software development cycle and how they can then use that to keep their customers happy.
A huge part of this is transparency - if people can see that something is on the backlog and working its way towards the top, or is in development, they're far less likely to get angry. If they ask for something on a forum and comments are made that appear to be a commitment without any further information given and no ability to find out for yourself without bugging the developers, that gets very frustrating very quickly for all involved (especially the developer who's being hounded by forum posts!)
To come back to your point - if there was a quick justification given for the decision to develop Zwave rather than Velux ("Sorry folks, we just don't have the capacity at the moment", "Sorry folks, we're talking to Velux to make sure we get this right, in the meantime we're going to focus on this Zwave device so we're not holding everyone up") then that would be miles better than just hoping that at some point someone might read a forum post and then a couple of months later publish a driver that meets the request.