I've just figured out how to use MTP with Amarok (a pretty complicated process, I'd say), and there's one thing that I noticed. If I upload a track to the device, it gets placed in the root of it. That differs from the way that synchronisation works on Windows Media Player, for example, where the uploaded tracks are put into new directories based on their tags. That's very useful when you have around 150 tracks and want to find one. Since I can see albums listed in Amarok's Media Sources, is it possible to do something similar in Amarok?

Which Amarok version do you use?

I've tested that with both 2.4.0 and 2.4.1. Too bad I can't find any RPMs with a build of 2.4.2, since that's where one of the most annoying bugs related to MTP has been solved.

There are on RPMs because Amarok 2.4.2 is not released yet. The probable release date is end of July.

The location the track is copied to is highly depending on the media device, not all of them handle the directories the same way. Sadly you didn't specify the model.

iRiver T10a. I've also noticed that in Amarok, when I transfer a file, in Local Media I can see both the artist and album, but if I reconnect the device, the album is shown as unknown. Artists are shown fine, however. Yet all of the files always go to the root of the device, and not in either a subdirectory of the artist or the album.

The output of mtp-detect is here:
http://pastebin.com/ipijhGzn

As for RPMs, they can be dynamically built from Git. Unfortunately, I can't find one for Amarok.

The problem with some iRiver devices is that those don't use a partition table, which of course can cause problems. See also this bug: https://bugs.kde.org/show_bug.cgi?id=275978

Since Amarok detects it fine, I guess that's not the case here. Either way it gets mounted on /dev/bus/usb/002/002 as it should, so I can't use fdisk to verify whether it has partitions or not (it reports "last_lba(): I don't know how to handle files with mode 20666").

Well, if it gets mounted on USB the it is in USB aka MSC mode, not in MTP mode, check that the settings in the player are correct.

Not quite 'mounted'. What I meant was that it's not mounted at all, but the device is at /dev/bus/usb/002/002. The player has no USB mode (although it can be enabled using different firmware).