I've never paid all that much personal attention to the Macquarie, Time. I own one, but I rarely use it, preffering the Oxford as my primary dictionary. (I nearly bought a fair-dinkum Shorter Oxford just before the GST on books came in. I should have done, damn it.) I sometimes run an aquisitive eye over my parents' OED but while I could live with the expense, I'm not sure that I like the idea of having to deal with that many volumes. Even the two-volume Shorter Oxford is a bit much.
I have no problem with the "legitimisation" of slang. It is not the function of the lexicologist to define language and set rules, merely to report it as accurately as possible. It is the job of the lexicologist to record slang, just as it is his job to record all other instances of language.
As for innacurate definitions, I'm not aware of any (being mostly an Oxford user), but I'd be most interested to see some examples so as to have some evidence on which to make up my mind.