I think it depends on what/where you're trying to clean. For smudges, splatters and fingerprints on the outside case of my machine, as above, Windex and a soft rag works fine. For baked on espresso gunk, I'll soak the part in espresso machine cleaner for a few hours or even overnight. If I'm trying to get coffee oil off of my backsplash (here's my original contribution to this thread...) I'll remove the cover in question, smear it with a coat of liquid dish soap (readily available in every kitchen and inexpensive) let it sit for several minutes then wash it off while scrubbing a bit with a soft rag. Rinse well, dry and re-install. If you're trying to remove scratches or pitting, well...
Besides, I don't want my machine looking
too clean, people might think it's never been used and I'm an amateur barista or some such thing!
