I have a 30GB iPod Video (5th generation) that I use with Ubuntu Intrepid. My music collection is larger than the capacity of my iPod, so I can't simply sync everything-- what I do is sync specific playlists. This, coupled with the fact that I view album art support a must, creates a specific need that not every program can satisfy.
I've tried out most of the popular players and IMO, the only one that really does everything properly is AmaroK 1.4. Here's why the others don't live up:
Songbird: Can effortlessly sync my playlists, is (AFAIK) the only program that can "restore" your iPod to factory defaults like iTunes can, BUT has no support for artwork (yet). This is a deal-breaker for me. Another strike against Songbird in my book is the fact that it ignores use Gnome's window manager and uses its own.
GTKPod: I have to admit I hate this one. The things you have to do to get stuff on the iPod are just silly. The interface is not intuitive. Also there seemed to be no easy (possible?) way to just sync the playlists I want-- I can transfer a whole playlist there, but when I update the playlist there is no quick way to sync the changes to the iPod. It does support artwork, however.
Banshee: Supports artwork. Does a pretty good job overall but again, no real "sync" feature. Like with GTKPod, I'm stuck having to drag and drop things I want and can't just sync changes to my playlists. This one is a bummer because Banshee is my preferred app for library management & playback on my desktop.
Rythmbox: Basically the same as Banshee with respect to syncing. Didn't bother to check if it will put the artwork on my iPod.
...which brings us to...
AmaroK: I'm not a big fan of KDE apps in Gnome due to the differences look and feel (especially ugly KDE 3.5 apps) but AmaroK 1.4 just does everything I want, the way I expect. It supports selective syncing (e.g. my playlists, even when I update them) and puts the artwork on the iPod. AmaroK 2 doesn't have device support yet, so I'm sticking with 1.4 for this sole reason.
If not for AmaroK 1.4 I would have to rely on a Windows app under WINE or VirtualBox, which would just add another layer of complexity to the whole thing. The biggest annoyance here would be the fact that I would have to edit my playlists to be Windows-frienldy (change every slash to a backslash in the playlists using a text editor) then save a "Windows" copy for the syncing player to use. This is on top of my current process which is:
1. Edit playlist(s) using Banshee, my preferred app
2. Export the playlist
3. Import the playlist to AmaroK
So even as it stands now, I have to do a couple more steps than I'd like (if only Banshee synced the way I like, I wouldn't have to bother with exporting/importing the playlists like I do).
"Why not use AmaroK for your music playback?"
Not a bad idea, and I actually used to do this-- but now that I have a burgeoning video library in addition to my music (for use with XBMC downstairs or playback on the computer in my room), I like that I can use one app for both audio and video.
So, seeing as 2009 will certainly be the year of Linux on the Desktop, I hope that this will improve with time. In the case of Banshee, which is currently under active development and becoming more and more popular, I'm sure that will be the case. I eagerly await future releases of what has become my player of choice lately.