I have a martin backpacker and I like it. Doesn't have the depth of tone of the D2 or the D28 I own but it is super easy to travel with and never seems to walk out of tune. I have traveled with it a lot and never had a single issue.
If I have to carry my Jaguar, Mustang, or my Yamaha electrics I use a roadrunner soft bag. It is pretty thick and it actually has two back pack straps instead of the over the shoulder strap (the guitar moves around with the shoulder strap). when I was looking at all the roadrunner bags I bought the one with the most padding. If you have to bring an electric on the road, bring a fender, Gibson guitars are too fragile to travel by anything other than hardshell case.
If I need a full size guitar I try to take the 1978 or the 1982 ovation balladeer since it is slimmer than a standard acoustic and if it gets chucked down the highway the fiberglass backs can sort of take the abuse (my 1978 slid out the rust hole in a friends trunk once without its case and it came out without a scratch. I got both my ovations from swap meets for less than $150.
If I need to take the other Martins or the Austin Dubro - I just take the car.
Whatever bag you buy make sure it has double backpack straps. The exception is the backpacker, it is so light if it shifts it is not a big deal, plus that shoulder strap can sinch down pretty tight when it is across your chest.