What is a very good Espresso machine

I second removing the entire group head for cleaning regularly. It gives you the opportunity to inspect all of the gaskets, and replace them if necessary rather than experiencing a failure. Planned down time is always a more positive experience than unexpected down time. I keep at least one of each gasket on hand for just that purpose. I wish I could chime in on the matter of back flushing, but I have no experience with the Gaggia's