The problem I had with RustFree was the fact that it won't dry. It was okay when you plan to store your blades in a plastic bag or so. But it will become a mess when you try to store your blades in a drawer, cases, padded bag (absorbent materials), etc.
I haven't noticed that. I've been using it on a 3V blade that I'm being very rust-paranoid about and so far no problems at all. I put it on veeery thinly though. Just a small drop on either side and smoothed around with my finger. Not gummy for me at that thickness.