Thank you Espiridion for you comment. I understand it, however I don't agree with it. You misunderstood Petrus1960, who was talking about just being an early adopter of this application. Your historical digression may be right, but it does not apply in this context whatsoever. Inbox was indeed one of the first apps to be available to the mac community once the GTD word did spread to the masses. And by the way, even if not reliable, it was promising. The authors made subsequent promises like it was raining, but they did not keep them. It's been ridiculous to listen to their enthusiasm and their "soon available" statements...
My half a star is a weighting of the characteristics: three for features and easy to use, half a star for both value and stability. Remember that this is not a really free app. It's intended to be a trial. It's the "state of the art" of the developers work so far, and it's far from being stable or feature complete. The developers are not going to maintain it, since the next vaporware update is claimed to be a paid app. So, all in all, it deserves half a star, and the judgement is based upon a long usage of the software.
I'm a licensed user of Inbox since 2007: as I'm used to do, I pay for the software I use, and sometimes even for the software I don't use but I find promising, to encourage development. But Inbox developers lied a bit too much to still deserve some credibility. They have to work very hard to get it back.

@Espiridion,

maybe it's time to close the thread ;) Your GTD historic erudition is impressive as Wikipedia is, but that's not the point: you are missing it and this does not help right here, right now.

I call it clutching at straws.

As I told you, I'm evaluating Inbox since it came out and I'm very experienced with it.

It's stated everywhere. It's also stated in this page, other than the developer's website. 2.0 is coming out in the AppStore, together with Duke Nukem Forever, and it will be a paid upgrade (truth be told, old users like me will receive a free upgrade [hurrah!]). 1.5 is not a fork, it won't be developed any further. So you can call it as you wish.

You should refer at the developers' forum for a better understanding of all the software's issues and unattended feature requests until now.

It deserves half a star. However, I'm eager to change my position, time will tell.

BTW, software is not a static cultural object. Its value cannot be understood without an idea of its progresses over time. No one will invest time or money on a software marketed as one hit and miss. There are better alternatives to such products out there.

No offense here, but I don't want to be your therapist!