Estel, I ignored your question mostly because you called my previous comments nonsense, so I wouldn't think you'd be interested in hearing more from me. Anyway, I don't have any hard feelings about it so here's my opinion on the matter:

There are two things I love on Maemo 5 which aren't very much related. There's of course some synergy, but one does not hard-require the other. The first is the fact that Maemo is almost a desktop distribution, with desktop grade apps (generally when having the N900 is almost like having your laptop with you, thing that I haven't experienced with any other mobile), and the other is that it's in a great deal open source. In that light I will disagree that Harmattan is on the other end of the line, as it's almost as open as Fremantle, with the exception of the swipe UI, which isn't a very big hurdle for development anyway.

Explanation of why those two aren't related: Let's say that Microsoft released a phone with windows 8 pro and intel processor. It would be very much a pc in the pocket, but it would be far from open.

On the pc-in-pocket aspect, we'll have to wait and see as this isn't something that you can know in the beginning, even the N900 was not very good at that when it launched, as it didn't even have a spreadsheet editor and other much needed applications. The BB10 build I'm using doesn't have a pdf reader for example, but I found a very nice app for the job, which works well, but doesn't integrate with the mail client to open pdf's directly. The good thing is that there is access to the filesystem so that hurdle could be easily worked around. I've even found a terminal application, python is there, but things like ssh are missing. Command line applications can't be built out of the box with the blackberry sdk but this could change in the future. Porting desktop Qt applications is easy so maybe we will see some of them. On the other hand Maemo had both GTK and Qt so it is once again a winner. Conclusion: The potential is there, we'll have to see what happens.

On the openness side, things are dark and grim. The OS is not opensource, (while some sources may be available since before RIM acquired QNX), the apps are not opensource, and there's no other way to run apps on your device than the store. So on your line with Fremantle and Harmattan it is far after Harmattan and in the gutter. On the linux standards front I can only comment that QNX is not Linux.

Some extra things. The software bloat is overwhelming. The people who put the full retail BB10 on their Dev Devices find the 1GB ram lacking, and even I have experienced apps shutting down on me when opening a few browser tabs. I understand that it has more than twice the pixel count of the N900 but 1GB ram should be enough.

Yesterday, I was searching for an old email in the Hub. The results were from the last month or so, and the mail I wanted was not there. There was no way to force it to get more mails. I took out the N900, and the laggy modest, happily fetched my required mail after a while. I can really put up with lag when I know that finally my job will get done.

The obscure "whose gonna ever need that" things that I've done with my N900 can only be matched by the N9, and not fully. For example last week I needed to open a port on the router in my office, so I ssh'ed -X in my computer there, opened firefox, logged in the router, opened the port and my job was done. Most "whose gonna need it" things that make the N900 special come from the legacy of the things in the software. X forwarding, Wacom X driver, kernel drivers for various devices, even the polish that Hacker mentioned is due to the use of mature desktop toolkits adapted to touch, and not things created from scratch. All those glitches that have been ironed out with thousands of lines of code throughout the years pop up again while you try to ditch the "dead" weight. You also ditch possibilities with that.
I don't have any hopes that these kinds of things will ever be possible with a mobile phone again, unless we do it here in maemo.org Mobile linux is going a different direction nowadays, not bringing linux down to the phone but trying to use the kernel as a basis for something completely different. The desktop linux stack on the phone will most probably die with Harmattan...