I haven't seen this concisely placed anywhere else in this list so
I'll go ahead and post what I've learned over the last few days
going from GCC version 2.95 to 3.2.2.

The big one is warnings generated while using ObjCopy when
attempting to link a binary file into the build. There are 2 sets
of warnings I got:

Warning: binary.o does not support interworking, whereas game.elf
does. (during linking)
I've read a previous post stating that you need to use the interflip
tool to remedy this. It turns out that I was link my files using
elf32-little so the tool wasn't working. Switching over to elf32-
littlearm resolved this.

Warning: architecture UNKNOWN (during .obj creation)
This one was resolved by placing a -B arm on the command line which
tells the tool that yes indeed the data is binary.

In upgrading, some code standards changed as well. We use 0 length
arrays for ROM loads quite often. We did this with
u8 array[0] = {d,a,t,a};

The newer version doesn't like this, but to fix it, all you need to
do is remove the 0. That fixed a couple thousand warnings :)

That's it for now. Just consolidating some info into 1 place.
The -B trick I haven't seen anywhere else so this should be new.

Mike