I have a couple of background apps such as Tasker and Glance for Pebble. They occasionally seem to get snoozed even though excluded but other than that the 8 is highly impressive. I'm pretty certain it is an app issue as it happened on the 3 and 4 rather than OS and it is significantly less pronounced and common on the 8.
The 6GB RAM helps it hold that much more in memory so, unless overly aggressive powersaving is in play, your favourite apps are there at a touch.
The only slow apps I have are poorly designed apps, or those that rely on ads from bandwidth throttled sites and I keep them to a minimum.
Zynga you have fun games but they annoy the hell out of me.
I have set mine to reboot early morning on a Sunday since a weekly reboot seems advised but even then Monday morning start-ups are nice and swift. The phone's anyway, my own less so.
Regarding the headphone jack I am glad they moved it to the bottom so I don't have to ensure the case has a cover for it. I lost my Note 3 for 4 months due to the headphone jack filling with water during a sudden rain storm and not outputting sound by any other method as it thought it had headhones in. I can't ever go back to wired after Bluetooth. Door handles are no longer a menace. That's when I got the 4.
On the bottom it is in the right place to use from my desk while the bluetooth set is on charge. I never thought of that before.