Guylhem,
Regarding the issue of what can be useful, I thought perhaps it may be useful if I put together a rough list.
1- The palm desktop for me is useful, also it would mean if I had a Palm, I could easily move to the Z without having to replace everything. The standard apps that come with the Sharp ROM can already do that. That ability would continue to be important. I'm not concerned about license issues, because a license already came with my Sharp. I would guess that I could easily install this application if it wasn't included in the distribution. Which would also mean that things like "today" would not be useful unless it replaced one of the applications. The key there would be "is it better, more useful, more feature packed, more compatible, etc".
2- Sharp ROM compatibility is great. It means that there is a huge library of applications that I can easily use. It's also why I keep finding myself returning back to the Sharp ROM. Quite a lot of software written for the 5500 work nicely with it. I will say that the idea of a "fast library" is very attractive in that it increases the useability and "adds on" a feature. Again, I'm not too concerned on the license issue as my 6000L already has a license (at least that's my impression).
3- a few applications on the Sharp ROM are a little obsolete. Rather than "replacing" them with another application, perhaps the idea of just "removing" them would be a good choice. If I decided that I wanted to keep that application, I wouldn't mind just installing it later on my own. Of course that best thing is if I could install it on my SD rather than my main memory. That gives me a choice, wihtout having unneeded applications. I guess a "barebones" thing would be attractive.
4- Libraries are always a pain. Knowing which one I need + which one works best is something that isn't the easiest. This is where your expertise I think is great. You've gone through all that and have tried to optimize it as much as possible. Multimedia is one area that would be useful. Specific instructions as to installing Kino and mplayer as well as the versions would be cool. I could probably live with it already installed. The only caveat is it seems that it's an evolving product. If there are specific tweaks you've done that are humbug, that would be a good reason to already include it.
5- Game emulators such as snes9x pose a small issue with things like keyboard mapping (instead of having to deal with a reverse keyboard). I'm not sure everyone wants to play games, but an easy process for this would be great.
6- GPS I think is a hot issue. Unfortunately things like gpsdrive doesn't work. I tried kstars on the OZ and it's a bit slow on the 5500. It is rather neat though, and is quite feature packed. I think things like this that were repacked into a fashion that would make it easy to install would be a nice touch. I think this kind of an issue is why people have been trying to get things like newer versions of opera going, etc. I suspect that Sharp ROM compatibility is going to remain a fairly useful issue for a while. This is where having a certain version of Opera already preinstalled is a struggle. On one hand, it does work. On the other hand, we're a little bit stuck. It seems wasteful to have to install another version if there's already a version installed.
7- Certain utilities that you popped in are indeed useful. The console for instance, is much more useful than the one that the Sharp ROM has. Those are the kinds of things that are a pleasant surprise. I think the idea of having a fast library is probably the most compelling idea. It allows things like games to run at decent speeds.
Comment: I think where I'm going is I really don't mind being stuck in the Sharp ROM world, because things do work for the most part. Your use of the fast libraries is a compelling reason to alter that perception --- provided I don't lose the current functionality I already enjoy with the Sharp ROM. I don't mind "new features" as long as I dont' lose much of the "old features".
Hope this rambling is useful ...