I got burned when I bought 4-5gb worth of generic Taiwanese RAM with unfamiliar chips. I had to take the vendor's word that it was CAS2 because the chips were impossible to research. Basically, I was sold CAS3 memory for CAS2 prices. I didn't verify this 'till months later, so the damage had been done.

Ever since that incident a year ago, I have been buying Crucial memory. I know I can trust them.