It's trying to go for a different type of launcher and system
interface. Some of the reasons that motivated me to work on this
came from issues I've had with the default UI:

- I want a way to be able to play and control music playing while
the device is in my pocket.

- Launching programs quickly is not as easy as it could
be. Finding the right button on the screen to push is difficult
to do quickly and I'd rather use hardware keys with feedback.

- In bright light, it's difficult to see the screen well enough to
turn up the brightness of the screen so I can see. Other devices
have had buttons I could hold to at least temporarily turn on a
backlight.

- I've realized I don't use any of the functions of systemui at
all. I map the long powerkey to softpoweroff and that's the only
thing I need to turn on/off the device. So the short power
button press is completely wasted for me.

What powerlaunch does:

It replaces systemui. It actually pretends to be systemui so that
it can interact with the rest of the system properly. It
intercepts the powerkey press that normally brings up the system
menu and gives the user the option to display whatever they want
instead.

All of the hardware keys (including power and home) can be bound
to do what the user wants (such as launch programs, lock the
device, reboot, whatever). It is extremely customizable via the
config file. The interface is also designed to be configurable
using glade.

There's an unlimited hierarchy/nesting of modes. For example, you
could map some arbitrary combination of keys like
left,right,up,right,right to launch your favorite program. Or you
could implement a device lock that requires entering the right
combination of keys to unlock.

It's probably easiest to just install it to see what it can
do. For example, I use it to go into pocket music mode by pressing
power,select. This immediately blanks the screen, locks the
screen, but leaves the keys unlocked. In this mode, I can
start/stop, change songs, and change volume using the hardware
keys (uses mpc to control mpd). Whenever I hit the cancel button,
it locks the keys also and is then in full softpoweroff mode. All
of this functionality is specified in the config file.

Installation:

I would recommend making sure you can log in via ssh to kill the
program if necessary, as it is possible to edit the config file in
such a way to make it impossible to close the program. And edit
/etc/mce/mce.ini to enable softpoweroff with the long power press
as softpoweroff will normally close powerlaunch (unless you have
told it otherwise).

- Install the deb package from
https://garage.maemo.org/projects/powerlaunch/
- Stop systemui as root with "sudo /etc/init.d/osso-systemui stop"
- Look at and edit /etc/powerlaunch/powerlaunch.conf (or you
won't have any ideas of what keys to press). Most of the
documentation that currently exists is inside the config file as
comments.
- Start powerlaunch as a regular user
- If you want to start it and run it in the background, try
dsmetool -o /usr/bin/powerlaunch

If you decide you don't need systemui like me, you can remove the
two init links /etc/rc2.d/*osso-systemui* (nothing bad seems to
happen).

You can edit the interface by using glade to edit
/etc/powerlaunch/powerlaunch.glade and specifying the particular
layout you want in the config file. This is probably the least
developed part of the program, but the eventual idea is to have
templates in the glade file and ways to fill in the template from
the config file (e.g. setting images of buttons to correspond to
the programs that keys launch as mnemonic aids). The example setup
has a not so pretty test interface that should show how buttons
can be handled in the config file.

Comments and ideas welcome.

Another solution to the included not-great-quality / falls-out-of-your-ear earbuds is to simply plug in your better buds of choice, but continue to use the device's case mounted mic. The built-in mic's compressor seems to be dialed up a bit high , probably so that the mic will pick up your voice as the device is sitting on a table in front of you (rather than right by your mouth.) However, this also makes the mic pick up background noise....but the overall audio quality/clearness for VoIP is quite good.

.....or is it made in a way to understand that the fourth connection is missing (from the mic) and doesn't disable the mic?
That is correct, sir.

Speaking about headsets, I never quite understood how to turn down the mic volume when using the voip. Is it simply fixed?
I believe it is fixed.