My Brompton dates from 2007 so is pre clip. I've become so used to it folding when lifted, and the ability to when I stop to just flip the rear triangle & rack under the bike to work as a stand, that I couldn't think of getting the clip "upgrade"
I've never had any issues with the fact the rear folds under when I lift the bike, even when doing the saddle on shoulder, running up the stairs thing. But I guess it all comes down to what you're used to.
The ability to fold very quickly is something I don't think I could give up.
YMMV
J