The backports kernel should make no difference to stability.
I was surprised the testing installer didn't recognise your network adapter so I did a little digging. I
think I found the reason and what to do about it, but no guarantees. I think the Intel network adapters which use the e1000 driver (that includes yours) often/always require non-free firmware in order to work. Debian doesn't officially distribute any non-free software/firmware which means it won't be found in the installer or the main repository even though it may be present in the vanilla kernel source from kernel.org. But there is a non-free package of commonly needed non-free firmwares in non-free backports (and in squeeze and sid). If I were you I would install using the regular CD1 or DVD1 and then obtain the packages firmware-linux, firmware-linux-free, and firmware-linux-nonfree and install them using 'dpkg -i <package_name>' and I would expect the network adapter to then be recognised on a reboot.
Another possibility to check before proceeding: if you have any live Linux CDs which do work with your adapter you can boot them and check which driver your network adapter uses and by unloading and reloading the module (driver in windows speak) and looking at the output of dmesg you should also be able to see exactly which firmware it requires. To find out which driver a device uses (on a Debian based system) you can run
To unload and reload a kernel driver you need to be root and run
Code: Select all
# modprobe -r <driver_name> && modprobe <driver_name>
then run the command 'dmesg' and you should see the name of the firmware and it being loaded. I would guess that the latest Ubuntu beta CD would be useful for this as it is Debian based and Ubuntu routinely include non-free firmware in their CDs.
