So I'm in the beginning stages (first 3 hours climb time) of my brand new Scarpa Booster climbing shoe. Let me tell you that I do not remember a break in for a shoe being so painful... and SOOO worth it!
Unfortunately I have the bad luck of having one foot slightly larger than the other (like most people I guess) and I have one foot that feels amazing while the other is on fire after the first 10 minutes in these shoes. Besides the pain these shoes really perform. Great edging with amazing toe and heel hooking grip, I just can't wait for these to be completely ready to go for a nice 5 hour bouldering session.
If you want performance in a shoe... these are great! If you want a comfy "marathon" shoe that you can lounge around in, skip them. Overhung problems and routes are no problem for these guys and I have never felt like I feet that could hold my weight upside down by themselves until I found these.
Look to the Booster if you want the La Sportiva Solution but your foot and heel just don't seem to fill in the dead space in the shoe. Happy Climbing!