Meb, for a while, ran with the sunglsases/earbuds combo when he was sponsored by Sony. He can't race with them, but they are good for training runs.
I am far from elite, but I can at least manage a 2:40 effort. I use an Ipod for some of my easier runs. Especially days after a hard track workout when I am desperate to just get through it.
As for what's on there - it runs the gamut of what's popular on the radio now and some old alternative/rock classics from the 80s and 90s.
When it comes to doing a tempo workout, I would avoid running with music. I like to think of tempos as trying to simulate the race condition. Half pace for 5-6 miles? 5K pace for a mile on, mile off? I don't race with music, so I try to avoid running a tempo/track workout with music.