Have you tried the timer app and how often do you use it? The timer app definitely is slower to launch a timer at times than watch OS 4.I also agree, OS 5 works just fine on Series 2. Battery life seems to be very similar after the update and after I turned off Walkie Talkie. Workout is slower to load but it was slow to load towards the later versions of OS 4 also. I don't recall it being as quite as slow to load on 3. I'm suspecting this is where the hardware is starting to show it's age but it's not unusable by any means.