With a break in study I've put some decent hours into this recently.
Have to say I found the Guarma section very disappointing. When I landed there I was real excited for a new map, new enemies, new animals and challenges etc however all I got was a shit chapter of uncharted then dumped back to the mainland. I haven't played online but I assume the area is an online map and this was just an excuse to show it off (that happens all the time in games now and it's annoying - you can spot an online map a mile off and it rarely sits right)
Like many have commented though I'm really starting to warm to Arthur now, they've handled the switch in his mind state beautifully. I know what's coming obviously but I really wish it wasn't