From the recent Rock Paper Shotgun interview:

"As far as how we feel about the sales results, The Witcher 2 is selling slightly better than expected (as of today, around one million units sold through worldwide). Our goal was to generate 30% better sales than The Witcher, and we’re achieving that. Given how the market has changed since The Witcher was released, I think this was both a realistic and ambitious goal. So we’re fully satisfied with what we’ve achieved."

:)

In an interview with Gamespot, during a gameplay demo, the CDPR guy said they had sold 1.5 million units of Witcher 1 (and I assume that was total sales up to that point). This was during the spring of 2011.

So considering that W2 sold 1 million units in a few months, it's good.