The Big Agnes product works pretty well when used for it's intended purpose. It is made for use in their sleep systems where you place the pad in a sleeve on the bottom of the Big Agnes bag you are using. I have had terrible time sliding off my pad when just putting a bag on top. I believe the horizontal baffles make this worse. I think that the valve on the Big Agnes pads is great and I am seeing more of this type in other brands. It is a two chamber flat valve. Air mattress for backpacking benefit from multiple overlaying of the air chambers for better comfort, less bouncing, and air integrity if done correctly. Make sure you get a pad with the correct R value for the season you are in. Warmer pads are marginally higher in weight then Summer pads. Remember that expensive, ultra light, pads will puncture as a matter of course and especially so in desert environments unless you are very careful. If you go out to the spiny areas of Utah, NM, etc., your pad WILL puncture.
When in the store, do the hip test. Lay down on a bag and roll to your side. If your hip bottoms out it is a no go. In terms of weight, the pad is not a great place to save weight. Comfort should your first priority, followed by longevity. You need your sleep so schleping a few more ounces will not hurt. Luckily these days the pads tend to get more comfortable and lighter at the same time as they decrease in weight.
In terms of specific brands, I like the Big Agnes when used as part of the sleep system. I do not like Klymit. The valve is sticky and I bottom out on the hip test.
Finally the ultimate pad, if you can use it, is a Thermarest Solar closed cell foam pad. It's bulky, but light, warm, takes lots of abuse, can be used for lounging, is puncture proof, but is not very comfortable for a geezer like me. If you can hack it, that's the one to get.
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