Are you kidding right? People, if you can't live with that response time, and you call that Lag, then please, return your Full of features and specs S5 and go with a Plain Vanilla Android Version smartphone or with the almost equally boring HTC One M8, and you will be happier, and all of us will also be happier reading less complaints about what we feel is the best phone out there.
Like I've mentioned before I had an M8, it lasted a week with me, Why?, Well, I gave it a try this time to HTC because they added an SD card slot, but for me Plain Android UI are simply boring and unattractive and HTC's Sense is, well, little better on the UI aspect but equally boring, I swear that the same day I bought that phone I was bored already. I gave it a couple of more days but there were a couple of things that I simply hated so it wasn't the phone for me, maybe for others will be the best phone, and I respect that, but coming here and complaining about lags and simply talking about Milliseconds of difference opening Settings and other apps is another story.
People seem to forget that Samsung's Touch Wiz brings Tons of new innovative features (some are gimmicks) but some are Pure fun and very useful, like Multi-Window, Toolbox, Priority Senders on Phone and Messages (That can easily explains the Milliseconds of difference opening them the first time Vs Nexus 5 or M8), Air View, Swipe to Call or Message, the whole Contacts (Phone and message) app, where you fully integrates and links all your contacts accounts, whole UI colors and animations, plus tons of other things that obviously, will take a lot more space and memory to be able to make it work, and MOST of us are very grateful to Samsung for think on what the user would love to have on their phones, and make that as easy as possible. This, without mentioning the Great Water and Dust resistant idea, Capacitive Buttons to not steal from the Great and Universally claimed as one of the best if not the best Display on any smartphone right now, all of this in an incredible Long lasting 2800ma battery that has been proven to last 7 hours of Screen On Time (In my case of heavy using of Web Browsing, Bluetooth, Emails, Apps and everything you may think of). It has it's faults, of course, it's not perfect, but all of them have some, but as I see it, nothing that can't be solved with a simple software update.
That's what this is all about, having everything we need in a phone, the masses speak for themselves, what is the most successful Android phone Series for years now?, The Galaxy Series with it's TouchWiz and their "lags", plus, if it wasn't for Samsung, do you think Android will be in the position it is right now?, you are kidding yourselves if you think the contrary.
Stop reading about lags on this forums, just keep using your phone and enjoying it, it's a Great, great phone, people do have issues and those need to be fixed and deal with it, but thinking on returning the best Galaxy Series phone that Samsung has built because of milliseconds opening an app for me is simply ridiculous. If you can't deal with these so called lags then just return it and go pick yourself another one, that's the beauty of Android, you don't need to settle for less than you expect, you will always have tons of options.