None.

Alexa is pretty much outdated, I'd prefer to see Analytics stats.
To start the conversation, I may check the stats briefly as they'll give me an idea of the level of traffic available.

Alexa can't speak to the quality or the targeting of that traffic.

They also get it wrong on many sites, especially sites that are a mixed bag or sites that are more "network" oriented in that, like QueerClick, they have different parts or micro-sites making up their sites.