Select Comfort/Sleep Number improved, excellent now.
(Seattle , Washington)
I have an i8 Sleep Number Queen bed. The company recently upgraded to adding zippers which now physically join the two air chambers. With the foam layers above the air chambers, and the air chambers being held next to each other without separating there is no "trench" effect.
I added a 2" memory foam topper, king size placing it directly over the air chambers and extending the extra width of the foam down the sides. This covers the perimeter foam, protecting them from being crushed much when sitting on the edge of the bed.
Now the i8 bed is hard to tell from a very good foam bed or top quality innerspring, but with adjustability and much longer life, with no deterioration of the bed. And its much lighter weight and very easy to move. And parts can be replaced if necessary.
The company will provide replacement air chambers that have the zippers for about $100.00 per pair, which is a heavily discounted price from retail, and worth it. Then the used air chambers can still be used, as for guests as a double bed by covering the air chambers with a full mattress cover.
Adding topper layers to the less expensive models also works well.
The 2 year warranty, including the remotes and pump is better than for most electronics, and the 20 year total warranty is better than most other beds.