There's a review of Network vulnerability assessment tools over at nwfusion.com
I thought it was interesting to see that there are several products in the review based on the nessus engine...
Also one point that intruiged me when I read it was the companies that declined to take part. Maybe it's just me, but when I read that it tends to make me think "I wonder what was wrong with their product" ie If you think that your product is the best on the market, I would expect that you'd be very keen to see it reviewed and recognised as such....
