this i have leaned recenly.

1) older version of the kernel may not work with newer version of gcc.
see post:

http://www.buoy.com/pipermail/lilug/2004-March/024154.html

so if want to used 2.4.17 i may have to use gcc-2.95.3
currently the uclibc gcc-3.3.x build process works well
and seems to build 2.4.26 of the kernel. so guess what
i am going to use these later version of the 2.4 kernel!

2) i dropped ptxdist and adopted a modded version of
gcc-3.3.x and ptxdist. life would probably be easier
if i just used buildroot out right but then i wouldn't learn
anything. so i slowly added to my "own" system.

3) atmel is not the choice for usb microcontrollers but
cypress. cypress has lots of inexpensive kits and extensive
user base. i found a nice usb dev kit for around 79
bucks.