La Marzocco Micra is up to temp in under 10 minutes and will stay there all day, it works very well indeed.

Do you know what is it that it allows for such a quick warm up? Small boiler? Saturated group? Maybe my comment is more relatable to HX machines then although I don't quite get how is it possible to warm up so quickly - the machine is still a 20kg piece and you can't beat physics with such large thermal mass.