The Pros
•Millions of dogs, cats, horses, llamas and other animals have been microchipped without any reported problems. (A few people have been microchipped too.)
•Thousands of animals have been reunited with their people after becoming lost or stolen. According to one microchip manufacturer, 10,000 pets are reunited with their people each month thanks to their microchips.
•Microchips work even after collars break or tags fall off.
•AAHA has created the Universal Pet Microchip Lookup site to assist vets, shelters and pet owners in microchip lookup and reuniting pets and their people.

The Cons
•Potential for injury or infection with implantation.
•On rare occasion, microchips have migrated to other areas of the body other than the shoulder area.
•Some animals have been reported to have tumors at the microchip location. Was the tumor caused by the chip? The exact cause has not been proven at this time.

I'm a bit peeved that those who haven't yet bothered may now get it for free when those of already responsible and organised enough to get our animals chipped had to pay £15-25+??

Still pointless IMO, it's unlikely to be widely enforced, not every pound/rescue/vet scans for chips properly, chips fail and migrate and it's not going to stop dogs biting, being stolen, lost or abandoned

It's the rest of the new legislation that dog owners need to be more aware of, how their dog is allowed to behave in its own home etc.

If it works like it does in other countries the cost actually went up when it became compulsory to well over double the cost when it wasn't. Also heralded the first stage of more expensive licensing and limits on dogs you can have.

My dog is chipped but there is zero chance of her going astray. Having heard about some of the potential (albeit rare) health effects, I wish I hadn't done it. In my case the risk v benefit calculation just doesn't make it worthwhile.
Also I fail to see how this will control dangerous dogs - which has been touted as one of the benefits.
OK I suppose they could have a go at the usual suspects providing they are allowed to 'profile' and randomly scan for a chip. But so far as actual dog attacks go, the owner is usually known, so identifying them is not generally a problem.
http://www.thebark.com/content/danger-microchips
http://www.dogsnaturallymagazine.com/microchips-pet/

I have two dogs and they have both been microchipped, but it caused a massive scar on my Vizsla. She is now 7yrs old, and you can still easily see where the entry point is.

Also, i paid extra to have a chip put in that tells the dogs temperature. The vet hovers the machine over the skin, and it tells them instantly. But still vets shove a stick up their bums.