I'm definitely getting closer so will answer part of my own question, but propose the next one.
The following is working (mostly)
uboot> tftp 0x1000000 uImage (its slightly smaller then 1Mbyte) uboot> nand write.jffs2 0x1000000 0x0 0x1000000 uboot> setenv bootdevice 0 uboot> nboot 0x1000000
At this point, I see:
Loading from NAND 256MiB 3.3V, 8-bit, offset 0x0 Image Name: Linux-2.6.17.11 Image Type: PowerPC Linux Kernel Image (gzip compressed) Data Size: 937470 Bytes Load Address: 00000000 Entry Point: 00000000
And then I get the uboot prompt back.
I had thought that giving the address to the nboot command would get me a bit further, but apparently not. Also, I should note that I dont have mtdids or mtdparts defined at this stage. My assumption is that we are doing a raw write and read from the flash and that the .jffs2 argument just deals with the oob (out-of-band) bytes in a jffs2 manner.
Charles