I thought about removong the lowers on my ultra for the summer, then got distracted with something else and it never happened. I'm glad it worked out that way.
I'm riding across OK in late June, temperatures are breaking 100 degrees. Sweltering hot, I'm thinking, why didn't I pull the lowers when I was thinking about it? I've got the louvers open, getting air flow, but I'm looking for every little bit I can get.
Three or four days later I'm riding up into the mountains in Colorado. It's 0630, the temperature is 40 degrees when I start up the pass. At the summit, the temperature is down to 32 degrees, and I'm thinking, boy I'm glad I didn't pull those lowers when I was thinking about it. I've got the louvers closed and it is blocking a lot of cold wind from my feet and shins.
Same thing works with the rain. Sure, they are a compormise, but they are way more adjustable than the other options.