I went into their new store in Sydney's Pitt St Westfields, and I must say, I was quite surprised at how realistic they looked. I had my ring up against them, and there definitely wasn't the "glassy" look most CZs have. I am pretty good at picking real and fake, and I was challenged.
That being said, I think going and buying a 3-4 carat fake ring, you can clearly tell it is fake. Your *average* person (I use this term very loosely and with no intention to offend anyone) cannot afford a decent diamond that size. You are going to have to compromise on clarity or colour somewhere along the line.
They have a few cute pieces, but I thought the gold they were set in wasn't very nice. The colour of yellow gold just looked off a bit, and honestly, if I was getting a CZ in white gold, I would set it in silver.
All in all, I am glad I have a *real* diamond in my engagement ring, but if I was on a tight budget, I think the secrets stones would be an awesome alternative!