That's about as flimsy as it gets. Old G80s are flimsy too, since they have no metal plate. Newer G80s have really thin, light cases, so they're even flimsier than old G80s.
However, flimsy=/=bad. Old G80s are my favourite kind of keyboard. I much prefer them to Filcos, etc. PCB mount switches feel really nice in my opinion. I've never tried a new G80 though.