I got Millenium Quiheads for my first shell set (1x 10", 2x 12", 1x 14", 1x 20") and later on two more sizes (1x 13", 1x16") for an additional floor tom and a new snare, to replace the regular heads with them for my home kit. Overall, they are a good purchase for their cost. Below is a detailed analysis:
1) Cost-effective: a good inexpensive alternative to the costlier mesh heads from bigger brands
2) Serve the purpose: extremely quiet heads. I play in my shared apartment, and never once did I get a complaint from my flat mates of being too loud.
3) Good fit: the fit matches the different desired drum sizes. The heads also have some headroom to allow for tuning high or low as per the rebound requirements.
1) Not very durable: these onesbreak/tear more easily than others. I have stopped using the bass drum mesh head since that one broke the most easily. Would not recommend if you are these ones if you are a heavy hitter.
2) Different rebound: the rebound is obviously not the same as what you would expect of a regular head, but that is the case with mesh heads generally.
3) Reduced sensitivity to triggers: I play with triggers in my home kit and get the audio output in my ears, and I feel that the triggers are a little less responsive with these mesh heads in comparison to others, thus forcing me to hit heavier, resulting in con#2 mentioned above.
Overall, it serves the purpose of making the kit silent, and is more pocket-friendly, provided you are not breaking them frequently.