For two people sharing, also take a look at the Six Moon Designs Lunar Duo. It has the typical "bathtub floor" sidewalls to prevent water pooling on the ground from flowing into the tent — and it's 54 inches wide. In comparison, the Double Rainbow in bathtub floor configuration is only 48" wide — and that's pretty narrow compared to most other two-person tents.
Henry Shire's website gives the lengths for the Double Rainbow in both clipped (bathtub) and unclipped (flat) configurations. However, when it comes to width, ONLY the unclipped/flat configuration is given — even though many tent users prefer a bathtub floor. I find this omission quite confusing, so I thought I would highlight this difference.
At the risk of stating the obvious, single wall tents made with non-breathable fabrics — such as the two tarptents above — perform better in temperate climes with low to moderate humidity. If you are interested in "all weather" three-season camping, then take a look at double wall tents as well. A perennial favorite is the REI Half Dome HC.