YMMV depending on what Android phone you want to compare it to, but it's still not 100% there, even in expensive ones.
That being said, it's not longer a deal breaker, I think, for most of the people that used to complain about it and if you have a pixel or a high end Galaxy its very rare to find instances of slugginess or dropped frames when scrolling.
I still face more sudden app crashes on Android than on iOS, weird error messages that are definitely not user-friendly and for some specific categories of apps, like games or sound/music, I still think iOS offers better selection and reliability.
Android user here, recently switched to iPhone 6 when my Nexus 5 died (will definitely switch back when Google Pixel finally arrives to Russia).
Here are my conclusions after using iPhone for a couple of months as a daily driver:
1. The switch itself was, unexpectedly, a lot less painful that I anticipated. All my apps and mobile workflows were up and running in half a day. So I guess I'm platform-agnostic.
2. iOS feels very smooth. No stuttering at all. Sometimes I get lagging, but it's a minor annoyance, not a showstopper - except for cases when I can't pick up a phone call because the round draggy thingy just won't drag.
3. App switching via double-tapping the home button is easy and pleasant. I like it more than the Android way of switching apps.
4. Text editing on iOS is absolutely atrocious. This is a major downside, and a deal breaker for me. That's why I'm switching to Pixel as soon as I can get my hands on it. iOS's magnifying glass cursor is much less convenient than Android's "handle cursors", especially when the text I'm editing is near the top of the screen. Going into the editing mode requires a long tap, as opposed to Android's regular tap, which is annyoing as well. The stock keyboard is slick but useless because I'm a gesture typer. I tried Swype, but it's no match for Google keyboard. GBoard might be a good replacement, but it doesn't support Russian yet, so no opinion here.
4a. The only thing in iPhone that somehow mitigates the awfulness of text editing on iOS is 3D-touch cursor movement. You strong-press in the keyboard area and drag, and the cursor moves. This feature is very well done. I'll probably get me iPhone 6s just to have it (not iPhone 7 because I don't like their new home button). Also, this 3D-touch cursor movement may not work with non-stock keyboard like GBoard or Swype - I have no information about that.
The one major area where I think Android leads (at least stock Android, Nexus, Pixel) is text input. The voice typing on android is significantly more accurate than on iOS, and has been my biggest hurdle in getting used to iOS. I know few people find voice typing practical, but once you get used to it it makes pecking out words manually feel incredibly inefficient by comparison. Also the android keyboard swipe technology works very well, and I miss that a lot on iOS. I know you can technically install third-party keyboards, but they tend to not work very well due to iOS restrictions, plus then you completely lose access to voice typing and I'm not willing to give that up even if it's inferior on iOS. Since switching to iOS from android a year ago, I still type significantly slower and with many more typos than on android. If I could use android's keyboard and voice typing on iOS it would be the perfect device.
I do find it annoying that you can't use voice typing on 3rd party keyboards, but I use gboard for swipe typing and then will switch to the oem keyboard when voice typing. It's not perfect (because the kb switch button doesn't usually go the keyboard I want), but it does work ok.
FWIW, voice typing generally works well for me. Not sure why you're having so much trouble.
