Ask HN: VC are calling later today, how much should I reveal?

We have a number of competitors in our niche. The VCs are calling us out of the blue, I guess to size us up, saying they are interested in the niche and us because we have a presence in it. I wouldnt mind the investment (though I've read about the downsides of VCs here and elsewhere), but I also dont want to give too much away in case they end up funding a competitor. What should I/should I not reveal? Plans for 09, new features, new customers in the pipeline, core competencies and tech, etc. There is no NDA at this point. Thx!