Do you mean automated testing, or automated tools?
Do I understand the question? Are you asking for pro's and con's to it?
What I would suggest is to browse some of the notes here and you'll find many of the industry experts, and lots of guru's talking about the tools, and all their features and functions, and how they compare to each other.
And if you look at the first note in this forum by Elfrided Dustin, 'Automated Testing - FAQs', you'll find a lot of your questions answered.
"Never doubt that a small group of thoughtful, committed people can change the world.
Indeed, it is the only thing that ever has." Margaret Mead
Automation testing pros and cons also is having a lot of relations to the application you are testing. If you are testing for an application which will be changed periodically, then regression testing is coming to picture. If a product is not having any changes within a short span then there is no point in going for automation. also the application which involves a lot of data driven testing etc..