Both my cats and dogs are microchipped, no swelling, irritation, or problems. Delgado had to be chipped twice because apparently the breeder's chip wasn't scanning
I look at it as a safety measure, extra insurance that if something ever did happen that the chances of them finding their way back to you is greatly increased.
The only downfall is to always remember to update your information always if something changes.
Jasmine - Female Miniature Poodle - born Aug 15, 2010
Loker Delgado Von Stalworth - Male GSD - born Jan 26, 2012
Koda & Zazu - 5 year old male cats
Alex - Male Cocker Spaniel (rescue) - RIP Cuddlebug 2007-2010