I hope that my comment and subsequent unrelated posts did not threadjack your post and interrupt further discussion on the matter thus leaving you w/o a suitable answer to your inquiry.
In view of Vicente's misunderstanding—in lack of a better word—I'd like to clarify that the problem I had was not with the existence or use of the expression itself, but with the use of the qualifier very. For me, a very common expression is one that everyone knows at the snap of one's fingers w/o much thinking. I asked a couple of Am. friends if they have heard it and they said No, they haven't.I agree with my dear Xótchi, I have never heard it to mean that. Not saying they don't use it, but wouldn't say that it's very common either. If it were, chances are, I would have heard it before.
Hence, I wouldn't go as far as to say it is a very common expression. I think it would be fair to say that—if anything— to boot is a somewhat common expression or a rather common expression as opossed to a very common expression.
I'd like to add that you will be able to do the math yourself on whether it's very or somewhat common based on the entries you get here. So far, two haven't heard it before, and one claims that is very common. Let's hear what other's have to say, so that you can come to your own conclusion.
However, your question was:
and the direct answer to it is: yes. Now, how often? That's another thingDo you use the phrase "to boot" to mean, informally, "as well" or "in addition"?