I'll weight in on this one since I just arranged for two tix the other day. I have a Miles 1 (Cap 1) Bus Card and it has NO annual fee.

Last week I redeemed miles for two tix for my wife. My business pays for mine. One to PHX on NW, the other to HNL on UA. Both times I had Travelocity, Orbitz, and the airline fares and itineraries in front of me coaching the ticket agent along. It went surprisingly smooth. In both cases I was able to purchase mine online and redeem hers for the same flights.

Previously,when I did not have the competing fares in front of me, they tried to push me into a higher fare and have me pay the difference. Be careful of that.

Putting that issue aside I think it a terrific program since her flights will earn miles and qualify for elite.