I've decided to buy this cute gaming keyboard, but before I buy it, I want to know if it will work (will it be compatible) with linux. Will work those additional 18 buttons? Will display work? Any help will be appreciated.

I can't speak exactly to your question but...I use this keyboard at home and work and the "cool" funtions don't work without the Logitech software installed.
As of this evening...not even on my new 64bit doz install. The software won't even install on the 64bit version so I'd guess we'd bot be more then lucky to have them working in linux.

If someone does have this working it would be great to hear!

Well I'm not too good with linux but I know there are drivers out there sourceforge.net has a few projects that make the LCD work and some that make the buttons work I have been trying to install this on Ubuntu 6.10 and being a very inexperienced person in linux I have not gotten them to work but many people have..

Also I have googled this and there is another site I will post up once I get home from class.

The site has Pictures of what the guy has configured the LCD to show ..

Sourceforge Links

The Search Results
Search Results for G15 linux

Specific Ones that Are for the keyboard itself
G15 daemon

G15 Tools

Those are the only ones I can find at this moment and at the computer I have access to.

*Edit

This is one of the few sites I found on google.
LCD proc

Thanks for digging them up but most of them need somekinda UINPUT support for kernel which in my case is NOT aviable (atleast google said so). Anyway will know that there are some nice gadgets for G-15 and linux

The best way to tell if your system has the UINPUT driver available is to run:

sudo modprobe uinput

If it doesnt complain, congratulations, you've installed the uinput driver into the kernel