Different timings compatibility?

So I have 2GB of OCZ plat memory and now there are some good rebates available and I am thinking of upgrading to 4GB.

However the current plats on the market are Rev.2 with different timings, will I encounter problems by mixing the two pairs?

Likely, I believe they have different IC's. Best bet is to contact them directly to inquire about the exact same Rev that you currently own.

I would say you could mix and match, but your timings will be limited by your worst stick...maybe even more so