Singles:
Love This Feelin' - 6/7/8
HACK - 5/6/7
R5 - 4/7/9 (AN EXTREMELY DIFFICULT SONG ON HEAVY! BE CAREFUL!)
Real - 4/6/8
Waverer (Slide Mix) - 4/5/7

Doubles:
Love This Feelin' - 7/8/9
HACK - 4/5/8
R5 - 5/7/9
Real - 4/6/9
Waverer (Slide Mix) - 4/5/7

Love This Feelin' is incredibly old and was last seen in the U.S. in DDRMAX. By all means not very spectacular, but I like the guitar riff. Waverer is actually continuing the newly made tradition of transplanting songs from Silent Hill, in this case being Silent Hill 4. R5 and Real are beatmania IIDX transplants (probably HACK too).

Also, I would like to take the time to tell you all that I have submitted (and fortuneately, got approved) a profile for the upcoming PS2 release of In The Groove. I won't say much here and you can just read the profile yourself, but I can tell you it continues where DDR left off in terms of difficulty: http://neoseeker.com/Games/Products/PS2/in_the_groove/