Now if I could just make up my mind between Solo and Sky5100 I could get the ball rolling!
After using a solo/approach combo during a 3 day backpacking trip recently the question of solo vs 5100 for me would boil down to the season I was planning on using it for. Late season, where more insulating layers, stouter sleep systems and calories are required I would definitely go with the 5100 (or greater). Early season, where I could get away with a lighter bag and shelter, the Solo would be more efficient for me. Considering that, the 5100 seems more versatile as it is can convert down to the solo ci @ a min weight cost. Also, I could see the full length front zipper, internal pockets and lid being nice features.
Either way, in the limited use I have had so far, both the Solo and Approach have been great. I opted for this combo bc I like having the approach as a day pack and not dealing with a bigger pack cinched down. I am also tinkering around with an Eberlestock scabbard between the frame and approach bag to see how that works in day pack mode. The modularity is great.
For what its worth, I also opted for the 3 piece belt (33" waist) and it worked out well for me with a 52 lb load and 32mi trip.