Well not had cause to use one recently, I had one to tape lectures (no problems) however I found that car salesman weren’t too keen,which gave a good indication of which one to buy from, that was a very interesting exercise!
I used to use a small digital (Olympus, still have it), and have a small tape machine in a drawer somewhere.
Like maude, I think that you should ask before recording (it might even be a legal requirement), but it is similar to taking a witness along with you.
If they have nothing to hide, then they should not object.