I used to be a bottle guy but in 2019 moving up in Cat the races became longer requiring more than a single bottle. So I relented and moved over to the USWE packs. I wouldn’t say USWE is the most comfortable out there, but its comfortable enough, a minimalist design and it just plain stays put and doesn’t bounce or loosen as the bladder empties. I also like the access to the jersey pockets to get to gels and other quick supplies.
If you dislike backpacks in general I don’t think an USWE pack is gonna change your mind. However, if you’re needing to move to a backpack and/or you felt a hip pack (horizontal) had some limitations, I’d say give USWE a try. Otherwise you’re probably better off to sticking to a design you know you like.