Robbie is right. Additionally, singing through any harmonizer requires an entirely different approach to your vocals - it's a completely different art than just belting out a song with a powerful voice through your hand held mic and using pull away techniques. Voice control is of paramount importance, yet it is often completely neglected by the singer when the vocal harmonizer comes into play. And, because every voice is different, it's just not a plug and play device - even the TC Helicon Harmony-M or the Digitech VR - I should know - I own a couple of both and I rely heavily upon my vocals. I can assure you that if you set up the VH2 properly, and utilize voice control, you can make it almost, but not as good as any outboard harmonizer. The difference is so insignificant that no audience would notice.
All the best,
PSR-S950, TC Helicon Harmony-M, Digitech VR, Samson Q7, Sennheiser E855, Custom Console, and lots of other silly stuff!
K+E=W (Knowledge Plus Experience = Wisdom.)