What about the use of Bitwage? Been on their service a few months, and it's great, IMO. Not sure about their behind-the-scenes workings, honestly, but have had a great experience so far.
Discussion
i've not heard of them until now, but they don't seem to disclose who holds their reserves, meaning it's probably not them. they're probably using a reserves-as-a-service provider like primetrust under the covers.
Looks like they use Gemini to acquire the bitcoin. then there's a spread of 1%.