I have friends with kids at Lingnan, and altho its true they do not train you to get into the top local schools, many students have indeed progressed into the "traditional top schools" like DGS, St Paul's etc. I know at least 3-4 parents with sons/daughters in that league. The comment I received was that although it is true that the kids will have to work harder at P1 to "catch up", the parents did not regret sending their kids to LN because they were SO happy there.
My son has been accepted into Lingnan and altho I live on Kowloon side I am considering sending him there because the environment is very loving, plus lots of kids come from expat/english speaking homes, so I hve been told that English has never been a concern for these parents.