In my half frame bag, fits my whole tent + my tools + some energy bars. frame bag + handle bar bag + saddle bag is great, no panniers needed. and bike behaves nearly like a normal road bike.
Plus it may help bring back level top tubes, more frame bag space.
I do have to admit, for my race bike with no rack braze-ons, I used a seatpost beam rack, but a frame bag would have been nice for extra warm clothes or to put them in if it warmed up. But I had two bottle cages and used both, I would need to get a seatback rig for those.