What is your overall opinion of this product?
The Harmony Singer really does a great job of generating very human like harmonies. As long as you sing on key, it does the rest. The built in reverb is superb. The magic ingredient is the Tone button, which just makes you sound better. I attached the Harmony Singer to my computer and got all the latest upgrades, including a "less bright tone style" option (which really suited my voice and PA speakers). There is a gain switch to adjust the input gain for any microphone, and you can dial in as much harmony as you want for a realistic sound.
The harmonies are really well done and give you a variety to choose from so you can fit the harmonies to the song. I don't have any trouble getting the Harmony Singer to pick up the right harmonies, even when fingerpicking.
I suggest you check out the You Tube and TC Helicon produced demonstration videos, especially the 'girl with the green hair' on You Tube.