One thing that I find very fascinating about my iPhone... well, one of many things... is that it is constantly changing. Regularly my computer is downloading updates that make small yet fun changes to my phone, all of which are improvements. I cannot claim this for any previous phone I have had and I find it quite delightful and exciting, thinking that although the hardware of my phone may get out of date, the software will not.
Likewise, I recently downloaded the new update for iTunes which contains the new "Genius" function which I immediately ignored because it claims to put playlists together on your behalf and frankly, I can do that myself. But on a whim the other night, I let the Genius do its thing. I chose a song and let it create a playlist around it. I didn't even listen till the playlist until last night when I was at the gym (yea, I actually made it back to the gym. *shock* *awe* *gasp*) and I gotta tell you, it was pretty awesome! I'm sure it is simple to program, I mean it just grabs all the tags to your songs and then compares them, but I was definitely into the idea that if I hear a song that puts me in the mood to let's say run (;)), and then I want to hear other running songs it will do it for me.
So, stamp of approval given by theLAZE.
Give it a try. I think you'll like it too.