alandail said:

The Rio Karma has a little scroll wheel on the top right corner (think mouse scroll wheel). You can roll it up and down to scroll through menu options and songs. The Karma lets you drill down by Artist, Song Title, or Album (similar to iPod I suppose?), and you can then either scroll through all songs (or artists, or albums), or first choose an alphabet letter, and view only the tracks beginning with that letter.

I don't have a song count for you, but I know I have at least half (> 10GB) filled up, mostly comrpessed with Ogg Vorbis, and I don't have any problems finding the tracks I want to listen to in a reasonable amount of time.

right, but if you go to the all songs list, or any play list that has a few hundred songs, do you have to keep lifting your finger and roll the wheel again? Right now I have 190 songs in my playlist Best of Prince, which is a smart playlist that just adds prince songs I rated 5 stars. If I am listening to that playlist and decide I want to listen to Xenophobia and it's currently playing Adore, isn't it going to be a pain to scroll down without the scroll wheel? How many songs can you even scroll through with a single motion?

alandail said:

I see what you mean about having to lift your thumb. The Apple design is very innovative in that area. After playing around with my Karma for a little bit, though, I can say that it's pretty good too. As you spin the wheel faster the playlist scrolling on the screen will accelerate. I would estimate that you can get through 50-100 tracks without lifting your thumb off the wheel. I tried a playlist with ~850 songs, and I could get from top to bottom with 8 to 10 thumb motions.

So yeah, not quite as nifty as the iPod, but still very functional.