No harm taken.
The synergy mainly comes from the one Gardevoir PL I run. With that out, you can pretty much attack with anything you want. It (along with Upper) also helps you keep pace with other, faster decks, by making some of your energies go farther. Also, the number of options you have against pretty much any deck is astounding. You have:
1. Sand Wall
2. Power Swing
3. Extreme Attack
4. Psychic Lock
5. Bring Down
6. Energy Burst
7. Psychic Protection (excellent in the mirror, or if you suspect a random Psychic Restore)
8. Sonic Blade
9. Psychic Cut
10. Hard Feelings
11. Hidden Power (lol seriously)
12. Lock Up (to force your opponent to kill Azelf)
13. Chatter (50 damage to Flygon, enough to allow Sand Wall to kill it next turn)
13 varied, damaging attacks. all at your disposal, pretty much whenever you want.