1. Heinlein is one of the greats.
2. Reading is highly subjective and personal, and the old saying 'one man's meat is another man's poison' very much applies. Stating as fact, rather than opinion, that a particular novel or piece of writing is poorly written, wonderful, boring etc, can be taken with great exception by readers with different views.
3. Amended number 1. I regard Heinlein as one of the greats.
4. DNF. Good grief! I think this is a powerful tool for anyone who loves reading. There are more wonderful reading experiences available than anyone could ever get through, so why waste time reading stuff that doesn't do anything for you?