I've only bought from there. Each time was a good experience. The only bad second hand purchase I had was from another site. I check it every day, but mostly buy from people I've seen here or on other boards.
I've bought and sold on DB - never a problem with anything I've bought; and excepting a short period of time a few years back when a troll was spamming almost everyone with DB listings, my sales have been problem-free.
Most of my purchases (and sales) are with PSers, which for me adds another level of reliability to each purchase/sale.
Like others, I check DB and LoupeTroop every day (if not more than once a day!)