I'm doing a review about the Dye i4 paintball mask, as I haven't seen one posted up yet, and I feel that I've used the mask thoroughly enough to do a in depth review about it.
Previous masks used: Dye i4, JT Flex, JT Spectra, Empire Vents Avatar, Grillz, Proto Switch EL, ILLusion bought Sykes AO2 mesh mask, JT Radar
Cost - ~$120
Extra lenses - ~$35 and readily available at local paintball stores
Time of use - 1.5 years
Packaging:
Let me start off from the packaging. It comes in a small box, which when opened, has the mask sitting on a pedestal like platform, under which has literature about the mask, warranty, etc. The mask has the amber HD lens installed, with a temporary lens protector. It also comes with a rip stop material bag to carry the mask in, to protect your mask during transportation to games. The packaging is very good, there is no way your mask is going to be damaged during shipping, some of the best packaging I've seen on any mask.
Description:
The mask is made from several materials - the jawline and mouth protector are made from a thick rubber, making it solid, yet flexible around the sides, so you can get down your iron sights, the frame around the lens is made from high quality plastic, and the foam that contacts your face is soft, and comfortable. The ear protectors are made from a spandex like material, which makes it flexible, strong enough to protect your ears from incoming bb's, but sound permeable, so you can still hear pretty well. The lens is pretty thick, making it harder to scratch. The lens is thermal, meaning there are two lenses, with a foam seal between them to prevent fogging.
The lens that comes with the mask is an amber lens, which apparently is HD, designed to make colors pop out more. Since I am a fan of clear lenses I never used the original lens so I can't confirm how good it is. The lens is built very well, the seal between the lenses is strong, I have not experienced fogging ever with this mask, in any environment (I play indoor and outdoor games every weekend. Another awesome thing about the lens is the field of view. Looking straight ahead, I have phenomenal peripheral vision, and I can even see my pouches on my vest if I look down, without moving my head.
Maintenance:
Taking off the lens is a breeze. It requires no tools, and can be done in about 10 seconds. also, the lens has only two points of contact holding it in, one under each earpiece, which means no damage to your inner lens, and no damage to the seal between your lens, which means your lens will last much longer then say, JT lenses, which have many points of contact, and removing the lens from the frame often causes a break in the seal, and fogging.
One thing to note - if you decide to buy this mask, try it on in the store to confirm that it covers your jawline.
Pros:
Very strong construction
Great face and ear coverage (again confirm that it fits your face type)
Unparalleled field of view
Great lenses
Flexible cheeks - you can see down the iron sights of any gun comfortably
Will never fog - there are vents around the mask to circulate air, the lens is thermal
Lightweight
Comes with an HD lens
Lenses are easy to find, there are many different kinds of lenses (tinted, clear, amber etc.)
Comes in different colors and camo's (the one pictured is called lizard skin, which resembles cadpat.)
Cons:
Might not fit your face type
Might be out of your price range
Conclusion
Overall, this is a great mask for airsoft. I can see myself using this mask for the next few years. I've been using the same lens that I had installed since the day I bought it, and it has almost no marks on it. I would recommend this mask to anyone who doesn't already have a mask, or to anyone who is looking to replace their "fog resistant" mask that fogs 24/7.
The mask is pricey for some, but you get what you pay for, and would you really trust your eyes to a $20 "airsoft rated" mask written in chinese that fogs as soon as you put it on? Didn't think so.
Photos:
Mask, with HD lens on the side, clear installed, with the bag

Side view of mask

Vents on top of mask

Face coverage

Ear coverage