Here's a small list, several songs of which I used in past reviews and are staples of what I use when reviewing.
Jazz - listening to Patricia Barber - Miss Otis Regrets, Light my Fire
Celtic - Loreena McKennit - Stolen Child, Lullaby, Carrighfergus (male singing)
Hard Rock - AC/DC - Cold Hearted Man, Let There be Rock, Led Zeppelin - All of my Love, Over the Hills and Far Away, Dazed and Confused, Pink Floyd - High Hopes, Shine on You Crazy Diamond, Comfortably Numb, Kansas - Hopelessly Human, Dust in the Wind, Heart - Magic Man, Barracuda
Rock - Meatloaf - Two out of Three Aint Bad, Heaven Can Wait, Supertramp - Rudy, Crime of the Century, Eagles - New Kid in Town, Hotel California, 7 Bridges Road
Classical - Choral music, Arvo Part (choral and stringed instruments), I have not tried a lot of full size orchestra pieces.
Folk/Country/Accoustic - Blue Rodeo - 5 Days in May, Dark Angel, Johnny Cash - Hurt, I Hung my Head
Misc - Sting - The Hounds of Winter, I Hung my Head, Lithium Sunset
OK now I have to be honest. I am going by memory in regards to the IE8 and MTPC as I do not have them on hand to do a true A/B test. But from memory and my own reviews I know what I struggled with the most with both those IEM's so can say why I think the GR07 is better. The bottom line is the IE8 were to dark and the mids to veiled for some of the music I liked best. When the IE8 worked they were stunning but when they didn't work well... they didn't work so well. In fact there are a couple songs I have listed that very well will sound better from the IE8 (I won't say which as it will be interesting to see if you have a similar opinion, one song in particular sacred the pants off me at the beginning when I first heard it on the IE8 but again I won't say which
). The MTPC was just to hot in the lower treble for me and the sound stage wasn't quite what I like size wise (little to small).
I also have to say I am a sucker for a bargain and at the price of the GR07 they are a bargain when compared to these other IEM's considering they retail for half or more the price of the other gear and are at least arguably as good as that gear.