I just finished the first instrument where I have used sinker cypress as tone wood. I am very pleased with the finished product. The instrument sounds wonderful and is quite pretty to look at IMO.
The top and back are sinker cypress, the sides cherry, and the fret board and end blocks maple.
My impressions of the cypress are as follows. It is very easy to saw and sands fairly well, except that the sawdust from this wood was kind of annoying in that the wood seems to be kind of "pitchy" which makes the sawdust stick to everything including the work, your tools, the walls, you, and your clothing.
The pieces that I bought are very pretty but I am unable to use them as efficiently as I had hoped due to quite a bit of checking. I am not sure if that is typical of sinker cypress or not. The price was not out of line though so I would consider buying more of the same given how well it worked out on this instrument.
I like this instrument well enough that I will be sad when it gets shipped off to its new home in the Netherlands.