****Amazing how musical taste can evolve.****
Yup! Sometimes, without even realizing it. I think it happens when we are open to the idea that our own musical taste is simply that, our own and nothing more; a certain amount of musical humility is a good thing. Then, before one knows it, music that sounded unbearable previously can sometimes become beautiful. It's about personal growth in our understanding of music in general. The process snowballs; before you know it, even "Lulu" will make sense and it's strange beauty can be understood.
The trick, however, is knowing when the music is simply not very good. That's part of the process too; after a while one just knows it and the judgment becomes more than simply an expression of our own taste (which, of course, will always be part of the equation; but, it will be in a better place). Jutta Hipp is, I think, a great example of this. I agree with you assessment of Hipp. Yeah, she can sort of get around the piano and she has a decent grasp of the language; but, with a definite (musical) accent. But, compared to the playing of the standard bearers, it's just not up to par. Hipp, in spite of her name, ain't too.
Finally had a chance to listen to the Ferrell clip; it can't be downloaded using an IPad and my wife and kids rule the computer :-). I did listen to a few other clips of hers that I could download. She is a phenomenal singer with amazing range and stylistic control. I had not heard her work, but had read a lot about her and, frankly, was suspicious of all the raves. She really is an amazing talent who can also write and plays the piano very well. Thanks for turning me on to her. I will say, however, that she strikes me as being at her best in a r&b or soul bag. Of all the clips that I heard of hers the one you posted, while really good, was not my favorite. This will sound as more critical than is intended, but I just don't think she is grounded in jazz the way that the great jazz singers are. To me, she is (in spite of her formidable vocal prowess) an r&b singer stretching out into jazz; the way Aretha does. The scatting (if one can call it that in this case) does not have the shape and structure of classic jazz improvisation. Not that it has to, but not only does it strike me as a little "over the top" as you suggest, but it just doesn't ring coherent for me. I think she has a tendency to overuse her amazing repertory of vocal calisthenics. Less would definitely be more in this case. Personally, I think she is at her best singing things like this:
http://m.youtube.com/watch?v=w2uD_MUu55U