It's old and bloated. It's on the low end of usability. It's not dynamic.
A few things I've noticed:
- Wish lists have to refresh to remove an entry
- The Cart will default to using your wallet even if you don't want it to
- Clicking the top menu options (Store, Library, etc) brings you to the last page accessed in that tab (a game page or cart rather than the Store menu)
- The Android apps run hella slow even on my 2013 Nexus 7 (attribute to bloat)
These are my core complaints. I don't mess with forums or Community in general, so I don't know how bad it is there.