First off, thanks and please keep going!
Current downsides relative to Firestorm
  1. Usually get the too may people using warning.
  2. Viewer default is super wide angle. For me thats far too wide. No idea how to change it.
  3. Graphics are very dark compared to Firestorm. The view looks "muddy". Was expecting PBR shininess.
  4. Keypad buttons don't work for movement.
  5. No AO, as I use Firestorm's. So, I walk like a duck.
  6. Head twists to follow the viewpoint. I'd forgotten how awful this looks. (This can be turned off in Firestorm (thank God).)
  7. Unable to use keyboard to enter text in chat. The viewer doesn't respond.
Not yet dared changing outfits, re-naming anything or teleporting.
As I said... these are niggles and there's lots of potential. Please keep going!