I've finally had some success with the most recent plug-in (Oct 18 17:26). I decided to follow Kurt's approach since he had started with the same problem as me, only being able to see Contacts and Calendars.
I used the newly downloaded 1.2.1 updater to restore my iPod. I then tried copying songs to it using MJ. The files uploaded but they didn't appear in on the iPod when it was disconnected from my PC.
I then used the option in the plug-in to format the iPod for use with MJ. When that completed I uploaded one album to the iPod, exited MJ and unmounted the iPod. Lo and behold the tracks appeared on the iPod.
I then got brave and sent a whole load of tracks, around 3Gb, to the iPod. This stopped fairly early on since the file naming system I was using, <track number> <track name> didn't like some of the live CD's and compilations I have ripped.
I renamed all my songs (~2000) to <album name> <track number> <title> using MJ (nice facility BTW) and started again.
I queued a combination of albums, artists and playlists to be uploaded. I was able to upload around 600 tracks before the plug-in said that a track already existed. This was probably because the track was in both a playlist and an album in the queue. I'm not sure if the plug-in allows you to upload a song twice, once in a playlist and once in another way.
I decided to give it all another go and formatted the iPod again using the MJ plug-in. I am currently uploading around 2.4Gb of tracks, all chosen by uploading an artist. So far they are uploading OK, although the process is a lot slower than with Ephpod. With Ephpod it takes around 1 sec per song (6Mbps). With the MJ plug-in it takes around 3-5 secs per song.
I also had a weird problem along the way. At one stage, MJ decided to keep on crashing on me with an exception violation :
Code: 0xc0000005
Flags: 0x00000000
Record: 0x0000000000000000
Address: 0x00000000028cd790
in Module 1 Media Jukebox.exe etc etc.
This error happened every time I sent an item to the iPod device. I resolved the problem by opening Ephpod. It said that it was writing Mac files to the iPod. Once that had done, I exited Ephpod and I was able to upload songs to the iPod again.
At the moment my main concern with the plug-in is how it handles tracks being uploaded in 2 different ways at the same time and how it copes with uploading playlists when some of the tracks are already on the iPod. Apart from that things are looking good.