Not exactly a dog - 5.0-5.0.2 had a memory leak issue, so as the phone kept running, day after day, more and more RAM was being set aside and unavailable, making the phone slower.
It's nice that Samsung is finally "addressing the issue", but it's been a known issue for a long time, and the actual fix is just 5.1 (which they evidently didn't start working on yet, being too busy doing things that look like thy're doing something, without fixing bugs that won't make the phone look any different, so the average user will think that Samsung sold them a phone, then forgot them. Keep pumping out those pimped-out screens, even if the phone crashes. People want cheap and they want new. "Working" isn't important - the lie of the day covers that. [Like "these things are so complex now that you can't make one without having a few bugs".])