Unfortunately you won't get anyone that has used both. I have a 640g and love it. I would hold off, as the new model 670g is about to make it's appearance. Although the only real advantage over the 640 is if you use the Enlite CGM, at least you have options. The new pump is out and has been released in the US about a year ago, has passed approval in Australia, but the sensors are still being approved in Australia, so it's being held back. The process in the UK is well under way for the approval. I was offered a pump years ago and I didn't take it, I wish I had the pump is not a problem and has so many advantages.