I have about 400 pictures stored on the SD card and it takes about 2 seconds to open, maybe a bit less. It takes maybe one second to open Calendar or Contacts -- about the same as on my OnePlus One, also with 3 GB.
Once in a while, I won't be able to swipe from the blank home screen to the next screen of apps on the first try. I don't know what that's about, but it only happens very occasionally, maybe once a week.
I'm using the 10.3.2.500 leaked OS at the moment, but what I've described is what I've been seeing all along. I have a fair number of Android apps installed, for what it's worth.