I have had some time to use the ds 10 plus and have found out that the song mode is the only feature different from the original (for ds lite). Though this is disappointing, it is quite fun. I went through the youtube videos and the websites trying to find some little difference (for ds lite) and all that did was make me want the ds-10+ on my dsi even more.
The song mode adds an element to possible live performances that were not possible before. You can now let a track ride out the 16 patterns while recording over them and they will repeat with the new sounds. this is tricky as you are used to the single pattern repeating (original version). For example if you have patterns 1-4 as your intro and 5-8 as a main melody you can record over 5-8 an octave higher (as they are playing) to give the song a not so repetitive vibe when the patterns are played the next time in your song. this also gives you the option of playing something live on the other keyboard or kaoss pad with the new patterns 5-8.
so you still have 16 patterns, same editing features, 100 pattern length etc...
yes, I will post a video sometime showing this if it does not make sense.