Many third party utilities (like Lenovo thinkpads, etc.) implement algorithms to increase battery lifespan (viz the amount of time you can use a battery, before you have to replace it), especially when laptop is plugged in to mains power - http://www.apple.com/batteries/
Battery lifespan is highly dependent on charging behavior - a continuously charged laptop will need to replace its battery more frequently than one with smart charging.

In linux, it has been available to a limited extent using the TP_smapi package, viz no longer available in Karmic (http://www.thinkwiki.org/wiki/Tp_smapi#Battery_charge_control_features)

The power managers should have options available to extend battery lifespan - it would be an extremely cool and useful feature for all of us who use laptops.

Many users have problems configuring their special keys in their keyboards. This is specially important for the ones migrating from Windows to Ubuntu: they do expect their keyboard to work in the same way it does under Windows.

As it is, a device (example: cell phone or pendrive) when connected mounts multiple drives if it has multiple partitions.

If you want to unmount a device with multiple partitions, you must unmount each one individually.

The unmount (safely remove hardware) should allow a ONE-CLICK option to unmount the device completely.

See the windows implementation here (with a card reader with 4 particions).
http://softporal.ucoz.ru/Images6/USBSafelyRemove_wm.JPG
http://2.bp.blogspot.com/_ruMCAJda6B0/R4sTELk8_9I/AAAAAAAAABc/Oq8qvjrOLF0/s320/ Portable%2BUSB%2BSafely%2BRemove%2Bv3_3_0_611.png

When you mount a partition in fstab, it's easier when you can read UUID from GUI instead of useing blkid. You can do it from GParted but it is not installed by default.

It seems very hard to find out information regarding drivers and hardware. For system device info you need to install the Gnome Device Manager, for proprietary driver info you need to view the hardware drivers application. Why cant these functionalities be one in the same? You could have one application that shows information pertaining to both.

Allow the mouse/trackball to be configured for eg left handed use, whilst retaining customary right handed use of the touchpad or second mouse

This would support multiple input devices, each specified differently eg speed, click response, primary/secondary buttons allowing better interaction with shared machines.

Also potentially usefull++ for accessibility where primary user has one input device and assistant/helper can use their preferred device, configured as they would wish

In my case, as a left hander I really like using a MarbleMouse, but the additional buttons are not recognised. As the laptop is moved around, sometimes I have only the touchpad, which, from habit I prefer to have configured with the left button as primary, ie right handed. Also allows me to share machine in these circumstances.

This granularity of HID configuration is available as a third party tool on other OS's. I haven't found anything on Ubuntu to match yet.

USB Speakers are becoming more popular as lower-energy options for external sound support on computers.

However, while Ubuntu Intrepid detected my usb speakers, choosing the spekers as primary in System > Preferences > Sound resulted in wildly inconsistent results, or else defaulted to the inboard speaker on my laptop.

I can only assume similar issues with USB headsets, as typically Ubuntu sees these as a supplemental audio device.

Currently, if one wishes to change the label for an external drive, say for example a simple USB Flash Drive, they must following this: https://help.ubuntu.com/community/RenameUSBDrive

It would be better if such a simple task did not require extensive command-line usage...
A very easy, and quite intuitive way, would be to allow the user to select the drive in nautilus' My Computer window, and rename it from there.
Finding the filesystem type and using the appropriate command could then be executed in the background (read seemlessly), by the OS, or some handler application.

This helps the user in quickly identifying his external drives, either in his personal PC or elsewhere, as opposed to just selecting mount points with serial numbers, which would only work locally on his own computer.

As I understand, system could distinguish one external storage from another. So, I think it would be useful to set unique after-plugging-behaviour for each device.

For example, I use 4gb apacer flash only for backup. So the only thing I want to do with it is to run appropriate script and then unplug.
Another my USB device is my 2gb transcend pleer. Every time I plug it, I want only to sync contents of my ~/music/2pleer/ folder with it. So, may be you could find some solution (preferably GUI-based) for this?

there are so many programs who mount on different way to mount files and systems. That is not Easy.

The unix Idea of "all its a file" could be more enhanced