I've used CodeSnitch on windows mobile 5, 6 and 6.1 devices with no problems.
Make sure you have the v1.4 installed and applied the v1.4 patch which is referenced here.
Like ctackle says, you need an older communications layer called CoreCon. I've also found CETK has CoreCon in it as well and it's not as big as eVC or Platform builder.
You need to setup the device connection settings to use ActiveSync (both transport and startup server), it does not seem to matter what the connection is called so something like Pocket PC will work fine.
The other gotcha I found is that you need to edit the codesnitch and procman shortcuts and add "/targetcpu:armv4i" to the command line arguments for them to work on WM devices.
I have also found them recently to be non-responsive to support emails as well :(