I have a mahogany Model A LoPrinzi concert ukulele. I bought it used, but did email Donna once, and she was great about responding to my question, even though I had bought the ukulele used.
Can't think of any negatives for me.
It is a little quieter than my other concerts, (smaller body might be the reason?), but has a beautiful clear tone, spot on intonation, very well built, and is a delight to play. The neck is slimmer, but is very comfortable, and I can play it longer than my other ukuleles without my hands needing a break.
It's a surprise to me that people here don't talk about LoPrinzis more. I think they are a great bargain. US luthier, reasonably priced IMO, well built, and great to play.