These are what I order and wear when in a customer's house. Cheap way to up your professionalism and build customer goodwill!

http://www.prosafetysupplies.com/c=UD3WF...hoe-Covers.html

In our country, each home has it^s own guest slippers, so if I have to take my shoes off, I always get one of them. During the summer time, it is not a custom to take shoes off here. In some other parts of the region, they take shoes before they even enter the main entrance, so that they do not make a single step inside the house with their shoes on. I do the same when working there, but it seems pretty silly to me anyway.

These go over my shoes. The shoes stay on!

It's a pretty good idea. I usually just kick my shoes off by the front door, but occasionally, when it is a cold floor, I'd prefer your solution!

Those slip on covers are handy for people who do service calls which involve a lot of back and forth to the car - electricians, plumbers etc. Maybe not so much for us?

I think it depends on regional customary practice.
Where I live, it is pretty customary to take off your shoes once inside the door. This suits me fine - I prefer tuning in stocking feet anyhow. Sometimes I'll even pop off my shoes when I am tuning in a theater or performance hall.

Me too. Once there was a journalist who made a short article about the piano tuner-me, with a photo. After a few days, I saw myself in the newspapers, tuning in a public library, with my shoes off. I forgot to take them on for the shooting.

I can't wear them. My left shoe is built up 2" because of an old leg injury.

In the homes of Japanese, Chinese, Koreans, I slip out of my shoes even though it hurts my back to walk very far that way. Usually though, they stay on.