I think they are great and it is true that they can be helpful. A lot of shelters now have the scanners so that they can easily find the owners (provided the owners did their part) instead of holding the dog and possibly adopting out or having them PTS. (Some shelters only keep dogs for a few days sadly).
I use multi ID for my dogs chip, DNA profile and tattoo.
My puppy is microchipped but she hasnt gotten lost yet. I agree with microchipping.
Its not painful, its extremely useful, its easy to put in.
It can migrate easily so it needs to be removed and re-administred, you need a new one when you details change, depending on who its registered with it can be costly. Even with these cons I think its worth it in the long run
Not sure which chips you are familiar with nor where you are a located.
Here in the US (if you are elsewhere?) there are a couple main brands.
They are painful to insert, some react more to it then others. I'm sure to some it is more painful then others too. The needle is quite a bit bigger then that of a typically size used for a vaccine and the way it is inserted and twisted in can't be pleasant.
They can certainly migrate so you could have yours scanned for as often as possible. Say by your vet at check ups, to see if it has migrated or not and if so where it is.
There are basically 2 main companies here. Neither of them require you to get a new chip when your info changes. You simply update it with the correct info. I've never had this experience of having to insert a new one.
Neither are expensive
HomeAgain is $17.50 per pet
Avid is $18.50 per pet and they also have an option of doing 5 dogs for $50 which makes it a real good deal $10 per pet.