Daniel Choi would disagree with Sen. McCain. As Think Progress notes:

Choi isn’t alone. Since 1994, DADT has resulted in the discharge of more than 13,000 military personnel across the services, including approximately 800 with skills deemed “mission critical,” such as pilots, combat engineers, and linguists. According to a 2005 report from the Government Accountability Office, “the cost of discharging and replacing service members fired because of their sexual orientation during the policy’s first 10 years totaled at least $190.5 million — roughly $20,000 per discharged service member.

It’s unclear how these facts led McCain to conclude that the policy is “working well.”