This is my first lute, so I had it inspected by a professional lute builder (40+ years of experience, built instruments for and hung out with all the big names in the lute world) and he was very pleasantly surprised by the build quality, sound and playability of the instrument.
I have replaced the strings with Aquila Nylgut, and I have replaced the frets with gut frets, which made it sound a lot better than the nylon strings which came with the instrument.
We also modified some things, but be careful since this probably void the warranty. We have drilled new holes into the first, seventeenth, eighteenth and nineteenth string pegs which allows for winding the strings outside their respective peg boxes. This way the strings travel in a straighter line and it’s easier to tune the instrument. We have also shifted the strings on the extension neck by filing two extra string slots to the right on the wooden nut (the nineteenth string sits in the slot of the seventeenth now, 18th in the 16th etc.), which also allows for straighter string travel, and also the strings do not rub against each other or against wood inside the pegbox.
Even without the mods it’s a great instrument, and I wholeheartedly recommend it.