Currently, the !mvn bang uses the search on
http://mvnrepository.com. Maven Central now has an official search service at
http://search.maven.com - could the !mvn bang be redirected to use the official one? !mvnrepo or something could stick around for mvnrepository.com, but the official one seems much more useful (better UI, stays up to date faster).
Looks like this formula should do it:
http://search.maven.org/#search|ga|1|{{{query}}}