There has been a lot of improvement in the smoothness since then, and they've actually had initiatives like Project Butter to make the OS experience smoother. That said, there are hiccups and stutters from time to time even on quad core 2.5 GHz 3GB RAM devices, and that's because of the way the OS is coded. There would need to be a ground up redesign to eliminate the micro stutters. However, I'm really magnifying a niggle here, and many phones will give you a perfectly smooth experience (especially the HTC One I'd say).
The smoothness thing is no longer an issue, but like some other tech enthusiasts, I find myself torn between iOS and Android. I use an iPhone, and will likely get the new one, but there's certain conveniences I like about Android. For example, I love how apps talk to each other. You want to send whatever type of file via Skype? You can! Assigning a file type to whichever app you want is no big deal, just like on the desktop. Background apps run awesome (like Dropbox uploads). Easy to copy sounds over and use custom ringtones and alerts in any way you want. If you have a camera with Wi-Fi and NFC, just touch it with your phone, it'll connect via Wi-Fi and launch the app right away (doesn't happen that way on iOS).
All that said, with Android there's no good backup solution, no iMessage, AirPlay, AirDrop, Handoff, Continuity, HomeKit or FaceTime, a less polished app and user experience, inferior app store, and numerous other niggles (like needing root for a lot of things), so each side has its merits, but the choice is no longer as clear as it used to be.
I tried the Android OS in 2010 and found it to have too much lag (choppy rough) for me. Has there been any improvement since then or does it still lag?