Twin Boiler machines have been gaining in popularity over the last coupleof years. Della Corte have set the standard, other manufacturers have now caught up (or dare I say) exceeded some of the earlier benchmarks. I am lucky enough to have had time working on Astoria's +4U when I was at the Trieste Espresso Expo. This machine has a large steam/tea water boiler then mini 1.25lt boilers for each group head. Each mini boile has two temperature probes- one in the mini boiler, the other in the group head...allowing for very minute tuning of temperature when making espresso. I am impressed with the progress being made by manufacturers and believe that anything that can help deliver a superior shot is certainly worth looking at.