Even If I say no, Alexa is a first thing I check when I get some new websites that impresses me. Although as a webmaster we have many different things to evaluate websites, for me Alexa is always first thing I check.
Its good as one of the metrics to check out, but its the only one used. There are over 20+ metrics that determine if a site is good or bad. DA, MozScore, Alexa, OBL, Referring Domain, # of backlinks, etc.... this can go on for hours
No! Why? --> Because it counts only people that visit your website and HAVE the Alexa toolbar INSTALLED!
Alexa could not exist without the participation of the Alexa Toolbar community. Each member of the community, in addition to getting a useful tool, gives back. By using the Firefox, Chrome and IE toolbars, every member contributes valuable information about the web, how it's used, what's important and what isn't. Alexa returns this information to the community as Traffic Ranks, Related Links, and a whole lot more.