Here is the email I had received from Mas Design, they seem to have great customer service with a response in less than a day/
Thanks for contacting us. Thus far, from the feedback from our customers, around 4% of the people have reported that our Ti backs affected the signal significantly, along with their wifi. They other 96% say that that they barely see any difference.
We are trying to see why some phone are experiencing this problem, while others do not. We have suspicions that certain production lot of iPhone are more prone than others, the way that the death grip issue could be clearly demonstrated on some and not others.
At our office in LA, and Bangkok, we have had no difference in our reception and wifi, whatsoever. There was 1 customer in Texas, and 1 in Florida that mentioned that their reception is affected. In general, if you live in an area with average to poor reception to begin with, I don't recommend you change to a metallic back, just to be on the safe side.
We went with a more robust frame, since the original target was for individuals that do not use cases. The back will be compatible with most bumpers, including vapors and elements cases. Tight fitting slip on cases and clear thin acrylic cases may not fit (for example Ozaki plastic cases), so keep that in mind. When we find a supplier with the same quality in the original size, we may fix this issue in the future.
We have a 14 days return policy (with a 15% restocking fee) for all those who chose to return their backs. Normally for us, if the backs have the slightest sign of use, they will not be resold, and we take a loss on them :]
I hope I this helps,
Sunny
Mas Design
Makes me a little nervous about reception. Element Case seems to have fixed this with the Vapor Comp, but I don't need another factor.
I was one of the early testers that had issues (I'm in Georgia, maybe Sunny is confusing me with Florida). I just got both of my MAS backs out to try again, and with my iPhone 4 naked I'm showing an average of -79dB for reception. Once either back is on, it drops to -98 to -101dB. That's about a 2 "bar" hit for me (I normally have 4-5 bars here). I love the way the backs look, but in my area, I can't use them reliably. I do know through talks with fellow reviewers in different parts of the country that it seems to vary widely with location. I have a friend in N Carolina who sees little to no effect from his MAS backs. It may have something to do with the band (850Mhz or 1900Mhz) that your provider is operating on in your area. They have different penetration (of obstacles like concrete, metal, etc) properties.