The shelter I volunteer with microchips all the cats, at 10 or 12 weeks for kittens. In fact I have held kittens while it is being done. It is much easier and less traumatic than a tattoo. Both of my girls are chipped and I will have my boy microchipped soon (they are all indoor, but just in case). My boy has a tattoo too, but it was done at the end of January and is half faded all ready. The vet said that was unusual and he would redo it but I'm not putting him under for THAT! He will get a microchip instead. I'm a believer, I think that they are very safe (never heard of any problems) and pretty effective! I once found a lost cat and he was traced back to his owner thanks to his microchip!
You'll have to keep us updated on your search for a cat. Like OsnobunnieO said, some shelters/rescue groups will take care of things like the microchip and spay/neuter for you so that you don't have to worry!