Actually I think youll find that Coffee Geeks have built this into a goliath, and David Schomer before them. Also Charbucks were using Lineas for a long time, and therefore a mystique developed. From a technical point of view, they are reasonably temperature stable and the GB5s and FB80 are temperature adjustable using a PID controller. Nevertheless, I think too much emphasis is put on the machine. Any decent barista using good fresh beans and a good grinder should be able to make excellent espresso on most commercial machines currently available. Ive seen this demonstrated again and again.
From a commercial perspective there are issues far more important that temperature settability/stability. Cost, reliability and maintenance schedule are probably more important.
Bottom line is that you shouldnt look at a machine to make good shots, but at the roaster and barista combo.