I bought a set last year after a very long 100+ temp ride through Georgia. I bought the Santa vest with 2 sets of packs. I got a collapsible waterproof double six-pack cooler at wally world. At night I freeze them (if I'm home) or do a 50-50 ice water solution if I'm at the no-tell motel. In the morning I put both in the cooler with ice and head out. When the temps hit 90 I put the vest on. After about 2.5 hours I swap the depleted one for a fresh one and let the ice do it's thing. At the first 300mi gas stop, I recharge the camelbak and re-ice the pack that looks the most depleted. I do this througout the day so I'm swapping out the packs about every 2.5 hours. As the day goes on, the ice doesn't fully recharge the packs as well as a cold soak and the respite from the high heat doesn't last as long, but it's still a lot better than suffering very high temps.
For those considering them, I'd suggest a slightly larger jacket as they add about 2" to your girth. At the end of the day, however, I feel more refreshed and less tired than without it. And since I'm filling the camelbak every fuel stop the time spent doing that is about the same as filling the cooler with ice.