I have been using a compact crankset on my single ever since they first came out and never looked back.
The 50-12 is a big enough gear for all the riding I do.
The 34-27 will get me up any hill even approaching 30%
Our current tandem has 52-42-30 front and 12-30 rear and I have never felt a need for a bigger gear.
Its rare that we spin out the 52-12 and at that speed (34 mph at 100 rpm) I don't need to pedal anymore.
So for the new tandem I am thinking 50-39-28 front and 11-28 rear.
This will actually give us a slightly bigger gear and same small gear.
The 50T will give us gears similar to our singles and will aid in front shifting.
Anybody else tried this?