I purchased my sureflap catflap approximately one year ago and I still love it!!
I deliberated between purchasing this or the competitor at the time and am so glad with my decision. The competitor was not only asthetically displeasing, but ran off the mains, so needed to be plugged into a socket, wouldn't work during a powercut (of which my area suffers from a few) and the sales pitch on the Internet was not only pushy but really weak and really made up my mind for me.
I have three cats in total - two normal size cats (4kg) and one 8kg beast! All of them manage to use the sureflap without any difficulties. I sensibly ensured that all of my cats microchips registered with the unit before fitting it to my door, all of which was really easy to do. That's it really - it's been working perfectly ever since and my cats love it! I have changed the batteries once in this time, when the indicator light came on and have not experienced any wear and tear issues - considering that I have three moggies it does get alot of use. I wouldn't hesitate to recommend or purchase another.
Now I am just waiting for a catflap to be designed that does not allow my cats to bring in mice!