My vote for the MEI Executive Overnighter bag. I like mine a lot. Potential advantage over the SkyTrain ('potential', as I don't own the SkyTrain, just read about it) may be that it has 3 compartments compared to the SkyTrain, otherwise quite comparable. Get a separate, padded shoulder strap off amazon.
Have my bag since a few months and took it on some international multi-stop business trips, up to 2 weeks in one-bagging spirit. Passed gate agents with ease.
What I do (and it always takes 2 minutes): When approaching the check-in as well as the gate, I hide the backpack straps again and just use the shoulder strap (or handle). When leaving the plane after landing, I convert the bag again into a backpack. A small hassle, but I imagine that this increases my chances to get past any gate agent otherwise inclined to make me check a bag the size of mine, or SkyTrain, or AirBoss, or the likes.