I finally got the Velo Orange Mojave water bottle cage and use a GSI Microlite insulated bottle for long rides in the Arizona heat. Before I found the Mojave I used 2 16oz Contigo commuter mugs on shorter tours where I knew it would be no more than 20 miles between services. On longer tours (especially out West), I went back to my 1 liter Zefal bottles. The good is that they carry a fair amount of water, the bad is that within an hour or so the water in them is the same temp as the outside air temp.
Now with the Mojave I can carry 1 liter of water that will stay ice cold all day. For longer tours I use a Polar and the Microlight with a 3rd bottle just as backup (with the possibility of additional bottles in my trailer for long desert crossings). This has turned out to be a very good set up for me. I've even filled the Microlite with coffee heading into a campground and woken to still hot fresh coffee. After 20,000 miles of touring I am still dialing in my ride.