Alright, it was asked for, so i spent yesterday tweaking 3MX to work with Ruben's 2.6 kernel. It isn't a "new" 3MX however. No new software added other than what was needed to get wifi and sound working properly with the new kernel.
The advantage of the new kernel:
MUCH faster boot time.
Machine no longer freezes if left turned on for more than a day.
Quicker and more stable wifi connections.
No more random characters getting spit out when typing.
Ability to boot from SD card.
The disadvantages:
Can not install to nand easily. (see below)
So to get up and running first download it:
http://filefactory.com/file/ca774a0/n/3MX-Ultra3-2.6kernel-rootfs.tar.bz2Partition and format an SD card with the first partition being fat16/fat32 and 16mb in size.
Second partition should be ext2 and at least 600mb. (or the rest of the cards free space)
Extract the rootfs to the second ext2 partition (as root user)
Then copy the kernel (uImage) from /boot to the fat16 partition.
To boot from SD card:
Hold FN+LeftShift, power on, (while still holding those keys) now hold F2 until you see X11 start.
To install to nand:
First boot from SD card.
Then: mkdir /mnt/nand
Then: mount /dev/mtdblock4 /mnt/nand
Then: rm -rf /mnt/nand/* (this will erase everything on nand1 so back up any important stuff first!)
Then: copy from the booted SD card the following directories to /mnt/nand (i use mc for this to make it easy)
/bin /boot /dev /etc /lib /libexec /lost+found /mozopt /opt /root /sbin /share /usr /var and the @linuxrc symlink.
Then: cd /mnt/nand and
mkdir /mnt
mkdir /mnt/nand2
mkdir /mnt/sd
mkdir /mnt/usb
mkdir /proc
mkdir /sys
mkdir /tmp
Now all thats left is to copy the new kernel to nand
cd /boot
cat uImage > /dev/mtdblock1
Thats it. Reboot and you have 3MX Ultra3 with 2.6 kernel installed.
Do NOT try using the F3 recovery console if you install this kernel to nand. It WILL destroy that parition. You've been warned

If you have a machine with 2gb nand then nand2 will auto mount at boot at /mnt/nand2. Anything else you will have to mount by hand. You can insert a card and run: fdisk -l to get the device names or check dmesg.
Cheers.