Who uses it?

Most political parties already use the alternative vote for their own elections:

Federal Parties Leaders

Conservative Party
Liberal Party
Green Party

Provincial Parties Leaders

Alberta Liberal
Manitoba Liberal
BC Conservatives
Most Green Parties 

International

Austalia - Members of Parliament
Britain - Labour Party  Leader 
Britain - Liberal Democrats Leader
Ireland - President
FIJI - Representatives
Papau New Guinea -  Representatives 

Cities
London, UK
Wellingdon, NZ
San Francisco, California
Aspen, Colorado
Mephis, Tennassee
St. Pauls, Minnesota  
Burlington, Vermont
Minneapolis, Minnesota

Sports and Entertainment

Academy Awarda, Best Picture 

Historically

Manitoba Provincial Elections.  1927-1953s.
New York City
BC Provincial Elections 1952-1953