I wonder if there's a tendency to move around a cycle of tent - tarp - bivvy as we get fed up with the limitations of each. I'm flirting with tarp at the moment, having enjoyed tent but chafed at the weight and the enclosure, and used a bivvy a fair bit but got fed up with the lack of space to dress / cook in the rain. I think tarp's going to be fun for a while, but come midge season I'll end up adding an inner, and then I'll be pretty much back to tent weight and enclosure. And so the cycle continues...!