Any one ever use the Comp. Engineering subframe connectors?

[Hopalong]

I have a set of these and am still conteplating using them.  I understand that I will have to cut the floor, which I am not totally against.  The only thing I am unsure of is that they notch into the frame rail, and I am not sure if I like that.  Any body have any experience with these?  Good or bad?