I own two Panasonic blu-ray players and they have all been terribly slow at everything, from loading discs to using the "smart" features like Amazon and Netflix. One of the Panasonics quite regularly requires me to cut the power to it and cold start it to either watch Internet content ("NO NETWORK") or to watch a movie (hang up with a "Loading.." graphic).
The Amazon interface on them also seems stuck in the stone age -- you can browse titles or search, but the 'modern' Amazon interface found in Sonys or the iOS apps isn't there so the Watch List isn't available.
HBO discs are the worst with these units due to their bloated menu/multimedia content. I just reflexively cold start my player before trying to watch an HBO disc.