Replacing the hints file with the top level zone speeds up lookups,
nope. there are less than 300 top level delegations, and a proper caching implementation will only hit the roots once a week per tld.
and removes the burden from the root servers:
wrong again. (consider the impact of all those axfr's, from millions of name servers, whenever the root zone changes.) but what it _will_ do is add one more config file which contains a dotted quad that might have to change some day. every few years a root name server is added or moved. everything is fine as long as there is _some_ overlap between your hints and the truth. but it's a whole lot easier to automate the change tracking for a hints file than for something that tries to make every one of millions of name servers into stealth slaves of the "." zone. i've set the reply-to to namedroppers, since this is really not a north american operations issue.