TL;DR: it’s going really well. I don’t miss the bag and it feels good not having a backpack. Some of the tools I am using to stash stuff on the bike are not great though.
A small Evoc under-saddle pouch: it’s OK, but it does stop the dropper post going all the way down, and that is annoying. The bag is really well made and surprisingly roomy, but unfortunately I need to find a replacement.
The Specialized Roll Cage bottle holder: garbage. It doesn’t hold the bottle I use, and I have a really annoying strap around it to hold the bottle in place. Its days are numbered.
Granite Rockband Strap: really good. My big inner tube and old school pump fit well and it is very stable. I do need something to protect the inner tube from damage.
I don’t know how I would find riding with a backpack if I wore one tomorrow.