I do not own a model 3, only a model S, so I do not have the experience of using the key card or phone as a all-in-one key. For my experience, I do like using the MS fob as the car doesn't auto present door handles 100% of the time. Sure, a lot of time I do leave the fob in my pocket and the car will respond, but if I want to get in the car without fail, I use the fob (button push).
I think the new fob for the M3 is a win. It appears to be better than the key card and I would assume for some it will be more more convenient than using a phone. Overall it appears the M3 key fob is a car shaped key card but now it has a transmitting range. Some people obviously wanted a M3 phone replacement instead. For these folks this key fob isn't for them.