This morning I synced my Windows Mobile 5.0 smartphone with ActiveSync 4.0 and noticed the Media Sync part of ActiveSync which I'd not noticed before on my WM2003 Pocket PC Phone (with AS 4.0).
 
Essentially the Media Sync simply integrates with Windows Media player 10 to synchronize your media to your device.  I've always ignored the media sync capability of Media Player 10, but with it integrated into ActiveSync 4.0 and a simple link that told me to complete setup, I thought I'd follow it through and see what it was about.
 
The Media Sync setup process was actually quite painless.  For some reason I always thought this would be a difficult thing.  The reason for this is that I dont keep playlists.  When I want to play music, I just select the album/artist/whatever that I want to play and hit play, then queue up a few others behind it and set it to shuffle mode.  So to sync my media to a device doesn't work with this scenario.
 
When I went through the wizard, it asks you what playlists to sync - it will list any of your own as well as any of the automatic playlists.  Most of the time I play the latest stuff in my collection, although sometimes I play the old favourites.  In terms of syncing media, this would probably correlate to the lists called "Music added in the last month" and "Music rated x stars". 
 
So I selected these two playlists and then noticed that there were options for them.  This is a good thing, because with the limited storage on the device (I have a 512 Mb miniSD card) you generally cant fit all the music in your collection, but you want to be able to limit the amount of media you sync.  The options allow you to set how much of each of the playlists you want on the device.  I decided that I wanted 100 Mb of the latest music and 200 Mb of favourite music.
 
This all done, when my music collection changes, it now automatically syncs new content to my phone and removes old content.  Nice.
 
Another feature of Windows Mobile that I love is the auto pause when a call comes in.  This is particularly good on the smartphone.  Yesterday I was sitting in the train station waiting to be picked up - I was enjoying the sun in the middle of winter while listening to some music on my iMate Jam when someone called me.  The music automatically paused itself, then the ringtone started.  Because I was using the headphones that came with the device, I just pressed the button on the headphones and answered the phone.  When I'd finished, I pressed the button again to hang up and the music automatically started again without me having to do anything else. 
 
On the Pocket PC this experience is only slightly diminished because the phone does not automatically turn off the screen.  I had the screen turned off while I was listening to music, the phone call then turned it on, so I had to take the device out to turn the screen off again.  Of course I didn't need to do this because the device would have turned off the backlight which is the main cause of battery drain in the screen, but still - I feel I have to have the screen completely off (what can I say - I'm compulsive).  On the smartphone, the device will turn the screen off automatically.  The way the smartphone and Pocket PC's work in terms of power saving (suspend on the Pocket PC is not impletmented at all on the Smartphone).  For more information on the power saving differences between the Pocket PC and the Smartphone is here (and it's an interesting read).