I use the stuff and we do indeed dump it down the sink with apprval of DEC
and safety officer. It is a proprietary mixture of buffers and minute
amounts of an aldehyde called glyoxal, if I am not mistaken.  We have to add
20% by volume of 95% ethanol to make the working solution by the gallon, it
is odorless and pleasant to use. Cytologic detail is usually excellent, it
does not penetrate organs well and does not harden tissues like formalin,
sepecimens remain soft and look raw sometimes  so grossing large specimens
can be a little difficult. You need to open bowels before fixation or you
sometimes get mush. I still use formalin to fix friable exophytic polypoid
colon tumors like villous adenomas which remain soft and cannot be gross
sectioned nicely. Everything else goes in Histochoice. Immunohistochemical
stains are excellent- no antigen retrieval is necessary for many common
antigens that require HIER or trypsin with formalin fixation:  keratins,
chromogranin, CD31, desmin. My ER and PR (run on the Cytologix Artisan)
require HIER with Nuclear Decloaker (Biocare Medical) for 20 minutes with
10-15 minute cooldown.
Hope this helps.

Jeff Silverman HT HTL QIHC
Pathologist Assista