That's an interesting assessment. I've actually been generally impressed with it. Loads fast, seems to be pretty intelligent about caching profile images and the like, and is generally pretty responsive (on a Galaxy S5). It is pretty handsy with the permissions, though.
I think the key to our different experiences is that you're on a pretty high-end phone. The real issues with the app become more apparent the lower-end device you have.
For example, I used to have a phone with only 1gb of internal storage, on which Facebook took over 200mb on its own (far more than basically any other app). It's pretty clear that whatever the devs are doing in regard to space usage, they're doing it incorrectly.
