--eliminates database owned by sa, and read only databases

sp_msforeachdb 'USE [?]; if exists(

SELECT Name, SUSER_SNAME(owner_sid) from sys.databases

where name = ''?'' and isnull(SUSER_SNAME(owner_sid),'''') <> ''sa'' and is_read_only = 0) EXEC dbo.sp_changedbowner...

DROP LOGIN [domainName\userName] is good for both SQL and Windows users, and deletes also related users, for me this simple syntax more usable than your SP.

doesn't work on case-sensitive servers