Pros
I joined Cardinal out of law school and it provided some patent-related experience to put down on my resume. Many of the HR people, docket managers, and SAO's are genuinely good people. You work from home.
Cons
Other reviewers have already pointed out many of the flaws, such as the completely random quality standards which depend on the SAO (search authorizing officer) that is assigned to your search, the general lack of compensation, the lack of benefits, and the lack of any paid time off (that includes weekends, holidays, vacations, sick days, etc. - if you're not working, you are not getting paid). I will add my 2 cents. During the time I worked at Cardinal, I went from making about 28k in my first year to about 65k-70k the year that I left. The entire time I was there I worked pretty much 6-7 days a week, for about 8-10 hours a day. It is true that eventually you do get more efficient at searching, but there is a ceiling to this and there is a lot of luck (or perhaps favoritism) involved. No matter how good you are, when you get stuck with a case with 200+ claims (this has happened to me multiple times), you are in trouble. These cases can take anywhere from 2-5 days (one case had almost 500 claims). Unlike the USPTO, there is no mechanism by which searchers at Cardinal can claim undue burden and reduce the search load. This means that from time to time, no matter how good you are, you will end up getting paid $300 (pre-tax) for almost a weeks worth of work. That's $60 a day, or under $8 an hour (assuming an eight hour day). Unfortunately, these types of cases were not a rare occurrence. I know this because at one point HR and management sent out an email to all searchers telling them that if they spent more than 30 hours on a search that they had to stop work immediately and notify management. This was most likely to avoid running afoul of any minimum wage laws. Think about that. This was such a frequent occurrence that it needed to be addressed at the management level.