I love imeem, but I think their user interface has plenty of room for improvement. One small thing that's really been annoying me recently is how scrolling through a playlist works. To see what I mean, try clicking on the "up" or "down" arrows in the following embedded playlist:
The scrolling increment (how much up or down the list moves when you click on an arrow) is way to small. Right now, one click scrolls the list about 1/5 of a song, so to scroll to the next song you have to click the down arrow five times. At a minimum, a single click should scroll the list by one whole song, but I think a more optimum increment would be 4-5 songs.