Ask HN: Interview with the competition?

I'v been working on a web site in my spare time for the past year. The big player in the market has some open positions. Sick of the day job, and thinking about interviewing with them. Probably wouldn't move across the country for this, but could be an interesting experience to see into this other company.

Not sure if could successfully monetize my little site, but I know I'm converting a small percentage of their web traffic to my site.

So the general question is, has anyone interviewed with the competition? Any hidden downsides to consider?